Seeking Advice: Friend asked me to be her bridesmaid.. her wedding is 4 months before mine

Hi! I am looking for some advice because I have just received a bridesmaid proposal from a college friend, but her wedding is only a few months before mine. It really caught me off guard, as I was not expecting this at all because I have only seen her a handful of times in the past 5 years. The thought of being in someone’s bridal party on top of planning my own wedding is pretty stressful and I’m not sure what to do. I’m worried about the cost of being a bridesmaid and the timing of things like her bachelorette. She lives in a different state than I do, so that would add to the expenses.

I’m scared to let her down and don’t know how to proceed. Has anyone had a similar experience?

Edit: both of our weddings are next year