How do I deal with my immature mom?

I love my mother very much but at times she can be ridiculously immature. When she gets angry in an argument she will often reply with "Psh whatever, I don't care." or begin to sing a song and pretend as if she isn't listening. What I will usually do once she begins to sing is walk away. But then she will start to sing louder in my direction, sometimes shout out the lyrics. She is 44 years old and it is strange to me how she can still behave so childish. I'm sure someone will ask "what did you do to make your mother mad?" I will honestly do nothing! I once asked her for advice and she behaved that way.