Wedding or not wedding?

I really need some advice. Me and my boyfriend are getting married on July 29th at the courthouse. It was the only date that was available and convinient for us. Also, because I have a beautiful baby on the way and we really wanted to get married before the baby arrives. The problem is, that my mom's 50th birthday is the same day. When i called her to announce our wedding, she just lost it like it was the end of the world. Calling me names and telling me that I should postpone the wedding and that her birthday is more important than my wedding. I really thought she would be happy and take it as a gift for her birthday, that her daughter is getting married... but is she right? Should I cancel the wedding and postpone it for another year...?