My friend needs to grow up. I'm starting to notice how rude she can be to me. Advice?

I'm really startying to debate my friendship with my best friend of 5 years. Everytime I say something she has to make a smart remark. One day there was a guy on the road trying to push his car and he looked like he had been tweaking. Also, we were on a tight schedule because we were going to a club and had to be there at a certain time time to get in because a friend of ours got us on the guestlist. I told my friend that we should go, and we were going to be late. The guy said he couuld use the help with the cops being around here. Which means he was probabbly hiding something. My friend told me "Stop being so mean" and she said really mean to me. And I got soo pissed I didnt even say anything. Then she said she didnt give a damn about the club, because that friend of mine had with her and then he had with me after...she said that loud infront of her sister, I got soo embared and pissed. And then later in the night I saw an unmarked car and said it looks like a cop but the