It is hard for sure. I have made friends with some families over the past years. Our children are friends, we go to each other's birthday parties, our children will go to the same school. It is a fine line though that you cannot cross. I had one mom who would often spend a good 30-45 minutes visiting some evenings. Some days I didn't mind it but others I just wanted to go. I usually would just keep things short and say that I have to go and get supper going or I would run and get the mail after work so it looked like I was going somewhere.
I would just have an honest conversation with her and you have things you need to do in the evening.