I'm not going to give a single mom a ride
Is there a reason why you don't want to give her a ride?
Because she's annoying, she's always asking for rides.
You aren't expected to do favors for people. If you don't want to help someone then you are within your right to deny them.
I'm going to be rude to her and tell her to get her own car or get a taxi.
You don't have to help others, but don't be a jerk about it. Just tell her that she can't depend on you for rides for too much longer, that she needs to eventually get her transportation situation in order sooner rather than later.