Im 17 she's 15 A LOVE QUESTION?

can a 15 year old really be sure there in love im not saying im the most mature person either meaning im absolutely sure i love my girlfriend i know i do id die for her hell id kill for her but im only 17 to others they might say you dont love her your just infatuated with her you just cant get enough of her right now your hormones are controlling you but i dont feel like they are im not with her to sleep with her we've already made love before but there was nothing sleezy or dirty about it she said that she wanted to pleasure me because she loves me it was a really sweet and caring event we dont do that often because our relationship isnt based off its based off our friendship we started dating not knowing how much we'd fall for each other and in the event of falling in love with her she's become my best friend and I hers we are comfortable around each other i can say anything tell her anything and she does the same she tells me everything i guess my question is can we last i know i love her but i feel like ive changed drastically from the age 15 im a completely different kid and my fear is that she will do the same become a different person and realize that maybe she wasnt really in love with me after all but just infatuated she tells me i treat her better than any of her old boyfriends her last boyfriend abused her mentally she started cutting she was really depressed when we first met now since we've been together i always see her smiling she was my first person ive ever had with and im her first as well she says she's sure she loves me whats your opinion?