Your Mom has no idea of your schedule and how busy your life is. She doesn't have a billion things going on, so waiting 2 hours for an e-mail reply is like an eternity. And maybe she's a planner and likes to know that everyone has the information and knows what needs to be done.... or maybe she's got anxiety about an occasion or event and this is how it presents itself.
I would just take a breath when you answer the phone. If she starts on her 20 minute tangents just tell her, " Mom, I really want to hear what you have to say and right now I have 20 things happening and I can't talk. Can I call you later when things slow down here?" And as far as the e-mail thing goes, maybe you don't have to reply to the message at length. Maybe you can just shoot a quick message that says...Busy day... I'll respond to this in more detail when I get a minute.
The holidays are a busy time and it sounds like you have a great relationship with your mom, but she has these little quirks. I think it's pretty normal. Remember to take care of yourself during these hectic days!
Happy Holidays!