friendship/relationships

I have a friend who always acts so happy to see me. When it has been a while she will say how much she misses talking with me. We have done things in the past together (we both homeschool), gone on field trips with our sons, etc. Her only daughter got married a few months ago. We were not invited to the wedding but were asked to help set up for it. It involved a 45 minute drive one way and missing a day of school for my children. (She asked us all to help). My husband said he wouldn't because he felt like we were being used. My 2 sons and I helped since I felt like that's what a friend should do. Since the wedding she has asked me several times to pick her sons up and take them to a tutorial that my oldest son attends along with her boys. The only time, anymore, that she calls is when she needs something from me. She does say that "we must get together soon" but nothing ever comes of it. Part of me wants to refuse to help her anymore but I don't want to be unChrist like but I don't want to be used either, which is how I'm starting to feel. We have helped this family with different things before. Her boys have come over several times to play but my sons are never invited over to their house. Any advice? Am I being used or being overly sensitive?