Should I Stay In A Relationship With My Girlfriend?

Ok , Im 16 .. My girlfriends 15
Everyday she tells me she loves me and she sends me big long txt messages explaining that.
But all her friends if they break up , their bebo pages have all like.. "I Miss You" bebo skins etc and quotes just to let the guy know that they want him back
But when we broke up for a few days my girlfriend just had "All i need are my friends , and a "Life Goes On" Skin..
I Honestly don't think she cares about me as much as she once did and I don't want to stay with her if she doesn't love me.
I honestly do love her .. what do you guys think I should do ?