Is this a reason to leave her?

i love my girlfriend very much; shes the first girl ive ever cared this much for, recently i was in a mental hospital for 3 days on a bunk suicide atempt because of how depressed ive been lately, i was hoping for support from my gf when i got out, she was acting normal and nice etc. but i looked at her myspace and she was flirting with a guy through comments, i asked her about it, and she said he was just a friend, but what she didnt tell me, was they went to a movie together with other friends, raved and took e together, and he started leaving her love poems on myspace, and callin her "his" and they were just flirting alot on myspace, also they were textin alot, she told me again she loves me and hes a friend, only. i begged her to stop being friends with him, and after a huge fight and after i cried she agredd, but then i found out she made a secret myspace for him, in which she told him things like your the reason for my smile, and what happend to us getting popsycles...i asked her about it, and she just cried and said she loves me that she sorry, a few weeks later, there still friends just like before, im tired of him, and tired of being insecure, this has broken my heart, is this reason enough to leave my gf? is she being shady?