Groper Girl

A female character who regularly gropes other girls, obsesses over their underwear and other open perversions. Strangely her targets rarely have long term animosity toward her and often remain her friend and only immediate violent punishment ever results from her actions.

Anime and Manga

 * Kuroko Shirai of A Certain Scientific Railgun regularlly lusts after protagonist Mikoto Misaka. She is a rare example that does experience long term animosity for her actions.
 * Tomoko Kuroki, the main character of It's Not My Fault I'm Not Popular! regularly gropes her only friend and peeks at girls panties while her thought balloons insist she is straight.
 * Homura of Puella Magi Madoka Magica is often portrayed this way in fan art and (to a degree) in spinoffs, but it's not in the original work.

Video Games

 * Katsuragi of Senran Kagura loves to grope the Gag Boobs of her fellow shinobi, none of which show long term annoyance at her actions and even express that they will miss the groping when she graduates. Her sidestory in Estival Versus has her learn to enjoy the rest of a woman's body as well, but it is ambiguously canon. Her main rival, Hikage, an Emotionless Girl, doesn't care about it, which Katsuragi varies between pleased with and disdainful (it's not fun if they don't react)..
 * Ayame, Katsuragi's kouhai who idolizes her, is also a groper. Katsuragi hypocritically freaks out when Ayame tries to grope her.

Web Original

 * Kizuna AI loves "touching" features in games, is fascinated by the thighs and breasts of virtual girls and attempts to manipulate the camera to see the panties of female characters whenever a game allows it. In her crossover with Arihara Tssubasa of Hachigatsu no Cinderella Nine she repeatedly tricks her into compromising positions and showing her underwear (Only to reveal, to AI's disappointment, she's wearing spats).