Territorial Smurfette

Han Solo: Hey check it out, it's another chick. The only other chick in the galaxy.

Leia: I don't like her.

—Family Guy: It's A Trap

Congratulations! You just received a new team member; and against all odds... it's a girl! Everyone on the team is happy to finally have a new girl to help balance out the gender ratios... everyone except for the sole girl already on the team! She isn't happy about the equaling of the gender ratio. Turns out, she actually took pride in the fact that she was the only girl on the team. The Smurfette doesn't take kindly to her male teammates gushing over the new girl, and takes great exception to her presence. As luck will have it, however, the Smurfette will end up being accused of just being catty because the new friend is a girl.

In stories where Status Quo Is God, you'll see the Smurfette turn out to be right because the new girl was either the Bitch in Sheep's Clothing or a Sixth Ranger Traitor, typically with only Smurfette to see through the act. In stories where there can be legitimate progress, the new girl will just be a target of shallow jealousy because the new girl is markedly more feminine or able to get along with the men more easily. In the end, the two women may end up becoming friends. Sometimes these two courses for the story get combined, leading to more interesting results.

A subtrope of The Smurfette Principle. Compare to the Alpha Bitch (who's just a territorial female, period). Almost Always Female, though a gender inversion may occur, especially in series that use The One Guy.

Examples of Territorial Smurfette include:

Anime

In One Piece, after Nico Robin joins the crew, Nami is the first of the crew members to voice her objection over Robin forcing herself into the crew. Robin manages to win Nami over quickly by giving her money.
- Usopp is much more negative about Robin, while less bitchy. And Nami's objection are reasonables, more due her "older sister" type friendship with Vivi (the princess whose kingdom Nico messed up).
Tengen Toppa Gurren Lagann: Yoko has some difficulty dealing with Nia when she joins Team Dai-Gurren, more because her Moe-ness wins over the guys than because of her being the Big Bad's daughter. They eventually come to terms before the Time Skip.

Comic Books

Marvel Star Wars: Princess Leia shows signs of this when a Fiery Redheaded wingmate of Luke's, one Shira Brie, starts flirting with him, although she gets over it. Then Luke discovers that she was an Imperial Deep-Cover Agent after unwittingly shooting her down during a mission; she survives, and eventually returns as "Lumiya".
- In the same series, Leia also dislikes Dani, a Zeltron woman who travels with them on several occasions and also has a thing for Luke. But after they work together on a mission this dislike largely fades.

Literature

When Wendy joins Peter Pan's group, Tinkerbell goes ballistic over this and gets Wendy shot by the boys.
Anabeth acts this way towards Rachel Elizabeth Dare, though it's mostly out of jealousy because Percy has clearly fallen from her.

Live Action Television

Carla toward Dr. Clock in Scrubs. Mainly because as a psychiatrist Clock was just as good, if not better, at being The Chick and began solving everyone elses problems (while, ironically enough, doing a study into exactly the same sort of workplace hostility while being unaware of Carla's grudge).
The Big Bang Theory: Penny acts like this a couple of times toward an attractive Girl of the Week who will usually be using one of the boys for something. When more permanent members Bernadette and Amy join, though, she's very friendly and bonds with them quickly.
Averted in an episode of the American The Office. When a purse saleswoman comes into the office to sell her products, Michael jokes that Pam will be catty to her since she [Pam] is no longer the hottest woman in the office. Both women are understandably repulsed by Michael's statement.
On Star Trek: Voyager, B'elanna Torres reacted this way toward Seven of Nine. It was pretty justified.
As feral on Mutant X are notoriously territorial, Shalimar did not take kindly to another feral joining the team. Per the trope, the new girl was a joy bringer everyone else liked. Worse, Shalimar was ordered to stay at Home Base due to an injury but was normally the I Can Still Fight type without two layers of jealousy for extra motivation. It turned out the new feral was even more territorial. She staged the accident that injured Shalimar then joined the team to finish her off.
Chiana in Farscape tolerated Aeryn, even seeing her as something like a sister (Aeryn was also on the ship before Chiana was) but reacted this way toward both Jool and Sikozu when they came aboard.
An episode of The Brothers Garcia had Carlos and Lorenna trying to join a band. The girl in the band (aptly named "Diva") protested against Lorenna joining because she wanted to be the only girl.

Professional Wrestling

Sharmel was the only woman of the main event mafia. She was rubbed the wrong way by Jenna Morasca buying her way into the group.

Video Games

Ashley of Mass Effect is critical toward Liara joining the squad. Though in this case, it was not specifically because Liara was female (...sort of...), but because she was the daughter of the Big Bad's dragon.

Web Original

In Red vs. Blue, when Agent Tex first met Sister, she was rather hostile toward Sister, even going so far as to lay down the law in a private conversation (which Sister, who is one of the Cloudcuckoolanders of the series, mistook as "you know, girl stuff").
Parodied by The Nostalgia Chick. She's The Ladette who doesn't know what a Chick Flick is at first and had a whole mini-arc about not wanting to do just girly movies anymore, but she'll still threaten anyone who dares go into her area of female nostalgia.
From Phelous's review of Stay Alive:"Im jealous of her cause I'm a girl"

Western Animation

Averted on Avatar: The Last Airbender. Katara and Toph clashed after Toph joined, but this had nothing to do with gender (Katara even liked having another girl around) and everything to do with Toph's standoffish attitude. Plus the fact that the entire Gaang was sleep-deprived at the time kept everyone on edge.
In Young Justice, M'ggan actually tried to befriend Artemis, but the latter ignored the former's efforts and openly ogled Superboy, M'ggan's crush, ticking her off. M'ggan still managed to get along with Artemis better than Wally, though.
Kimiko from Xiaolin Showdown reacted poorly to the addition of the mermaid Daeris to the team, mainly because Daeris had no problem flirting with the boys to get them to do things for her. Then Daeris taught Kimiko the same trick and they became great friends...but it was discovered later that Daeris was actually evil.
Lampshaded in the quote above from the Star Wars parody episode in Family Guy.
Inverted in an episode of The Simpsons where Lisa tries to pull off a Jackie Robinson Story and announces she's joining the football team. Only when she gets there she finds out there's three other girls on the team already and the coach is welcoming. Enraged she can't be the only girl on the team (or protest the use of pigskin footballs since they're entirely synthetic and the producing company donates to charity) she runs off crying.
Boom-Boom/Tabitha is the only girl in the Brotherhood house in X-Men: Evolution and when Mystique arrives back she leaves saying "too many girls in this house".