Weekend Road Trip?

I'm in a bit of a pickle here.

The Problem: My best friend wants to go on a road trip this weekend.

The Solution: Now that, my dear friend, I was hoping you could help me with.

I need help with making a decision. Most, if not all, of you don't know me, but I am a very, very, very indecisive person. This is probably because I tend to over think things, usually the unimportant things, which leaves me just downright confused.

My best friend would like to go on a little driving trip to Oklahoma this weekend as a sort of early birthday getaway. Lately, she's been feeling that once we move out to New York that we'll lose our freedom so she's been wanting to do a lot of things before we move, which I totes understand, but am not always too stoked about; like this slightly last minute road trip for example.

On the one hand, I would absolutely love to go on a spontaneous road trip with my best friend and little sister to Oklahoma, and wherever else our tires drive us, for a weekend. I think it'd be great to just have some time to relax and enjoy our time together because we all get along swimmingly; I guess you could say we're sort of like a tripod. Plus, this would count as her birthday celebration thingamabob so I don't want to be a bad best friend and tell her I can't go. ),:

On the other hand, I don't feel it's such a good idea to go on a road trip when we should be saving money for New York. The responsible monster inside of me is nagging me not to go because I need to save up money and try to be a responsible adult. Also, I'm not too sure if my mum would agree with this whole road trip deal because she's been pressuring me to be responsible as well so that's another miniature-ish problem. Why does adulthood have to be so complicated? -__-

Well readers, that is my current dilemma. I am leaning more towards going on this road trip, but like I mentioned, my cursed responsible side keeps getting in the way. >.<

So dear reader, I ask you for your honest opinion. Please, what should I do?