Regarding my girlfriends past

Me (M17) and my girlfriend (f16) have been together for a little over two months, i’m only now just learning alot about her past (directly from her, through social media presence etc). I’ve seen alot of stuff i really don’t want to see regarding stuff such as celebrity crushes, sexual fantasies and lots of quote un quote “young ho” stuff. i’ve brought it up to her and she plays it off, saying that nothing is serious, it’s jokes and she’s “changed” but there is a truck load of this stuff dating back to just days before we met. I’m not sure if my worry over this is just a result of insecurity or something else. (This is only my second relationship ever). Any advice would be greatly appreciated.