Am I wrong for feeling angry with a friend who did not tell my child happy birthday, or even give her a gift?

Here's the situation...My girlfriend and I have been very close friends for about 9 years now. She has 5 boys, and I am very close to her and her family. My husband, daughter and I made an effort to be at every birthday their family members have, and we have always given them a gift. I wouldn't think of attending a birthday without bringing a child a gift. We asked them to come over and celebrate our child's 12th birthday, but her and husband could not come because of a family wedding; however they sent their boys over to come celebrate with us...without a present! I am angry that she did not come by to tell my child happy birthday in person, and certainly angry that she did not send a present wih her boys. I wouldn't have been upset in the least if she did not give a present to myself or my husband...but to not send a present for my child after all the gifts I've given her five boys over the years really makes me angry! I know she didn't forget, because she sent her boys over.