Question about a relationship?

Hi this might be long but please answer. Anyways this is my problem my best friend lindsey wants to go out with me.. and i don't want to because of a few things shes moving away to go to collage and that's an hour and a half away but still she says shes gonna come back every weekend but i know that's not going to happen and. well last night some things happened we kissed and did a few things.. i didn't want it to happen but you know how it just does. were not going out and i don't want to hurt her at all and im 15 almost 16 in one month and shes turning 18 in the summer so my mom would kill me if she knew i was dating some one in collage but yeah does anyone have any advice for me please? what do i do i don't know what to do