So my friend lied straight to my face, best approach to still keep friendship?

So I haven't seen a really good friend of mine since her graduation party from her highschool (shes 18, im a 17 year old male who is now a senior). And we were supposed to hang out a little while after that (her grad party was exactly a month ago yesterday), but she made other plans and didn't tell me about them until last minute. I was heartstricken because I see her as like a sister to me. Anyways, I'm leaving for a month on Thursday, and we're supposed to hang out tonight (Wednesday night), but she told me on skype only a few hours ago about how she's going to bring me to a party and how we're going to have so much fun and stuff. First off, she knows I don't drink and I'm not a partier. Secondly, I feel lied to. Third, I feel like she's only bringing me to this party (a party of her close friends whom I don't know) because she feels bad that she basically cancelled the plans we were supposed to have. Do I go to the party (she says she's not going to drink,either,for several reasons)? Do I ditch her? What do I do??? Please help??!! This is an awkward situation I don't want to be put in!