My cats in heat and Im worried.

Question
My cat has been in heat for about 8 weeks now, and my vet told me that once they go into heat they go in and out like everyother week, so i'm used to her being in heat by now.  Last night she started acting really strange though.  She was screaming for about 30 mins.  Then she came upstairs from the basement and she couldn't even stand up all the way.  She was crouched with her back paws completely underneath her and she kept moving them, like she was dancing and couldn't sit still.  She was making a rolling purr noise over and over.  This is the how she has been for about the last 12 hours now.  Every once and a while she will scream a few times.  Is she in pain or is this normal? I'm worried that she's hurting.  I have an appointment to get her spayed in a couple weeks and I'm just wondering if I should try and take her sooner.  I have 3 other cats also, they are all steralized.  Can I let her around them?  I also have a puppy who will not leave her alone, should I make sure that my cat in heat (Star) is kept alone? I never got to this point with my other cats, they were steralized very young, so I'm not sure how to handle it.  Sorry for being so long winded, please try and help! Thank you!

Answer
When cats go into heat its very painful up until the day they get pregnant,  try and get your cat in sooner, and it might be a good idea to keep the puppy away from her the dog could get seriously hurt if it bothers her enough.  The other cats she should be fine with she can't get pregnant from a sterile cat.