I need some advice

Me M17 and my gf F18 have been dating for about 6 months now and she is going into college while im going into my jr year of high school and its been really good relationship and now she is getting ready for college thats about 30 min away but she isnt staying a dorm she is staying with her family house and so tonight she was showing me the stuff that she was getting some clothes to look cute in and so it was a bunch of crop tops, short shorts and some revealing clothes and look im not the type of person to control what she wears but getting all that for college and she says that she is excited for welcome week bc she will meet new people and go to the parties and what not and i do trust her but there was instant whenever i tried to look through he phone and she exploded on me but i dont know what to do and i just wanted some advice