How can I tell his female best friend to chill!

My boyfriend lives with 4 women in a 3 bedroom house. They are all extremely close and the girls are a rowdy bunch. Jan even more than the others. He's known Jan the longest, since they were in middle school and she's nice and all. Just gets too much for me sometimes. When me and him both walk to the dog she will jump all over him excited and then me and I'm really not a touchy person. She's a puppy in a human body. Then if nobody is there we can have our alone time but if not Jan is trying to talk to us and she talks so fast. I can't understand a lot of what she's saying but he's been friends with her so long he gets her language. It's not like I have anything to talk about with her. They're very all into musicals and she mainly talks about THAT! I hate musicals. My boyfriend said if she's ever being too much just tell her nicely to calm down, but he also said she's autistic so I feel bad. We all went the mall and Jan got in trouble for standing on a chair and she started to cry... I don't want to make anyone cry...