Suddenly having trouble with leg

Hi!
I have been a member of the preemie inspire group for a while, now my daughter has been diagnosed with CP so I joined this group as well. It's so nice to talk to people who "get it"! Zoe has been having this problem since Wednesday- we have an appointment with the CP specialist dr. for nov.11, but I'm wondering if I should take Zoe in to the pediatrician before that-
so, Zoe is 1 adjusted, was born at 30 weeks, 2 lbs, had an ivh with pvl on the left (affects her right leg and arm), and she can crawl (with 1 knee off the floor) and cruise. Usually, she likes to stand up while holding my hands, in fact as soon as she gets up she usually wants to do this. However, starting Wednesday, she doesn't want to bear weight on her right leg. I tried putting pressure all over her leg, hip, and foot, and nothing bothered her. Also, she still crawls and pulls up on things, but doesn't stay standing as long as she had been. What she WON'T do is stand holding my hands- as soon as I try to haul her up she gets a case of jello-knees.
Anyone seen this before? She is getting a hip ultrasound on the 11th. Wouldn't she cry if she had a broken bone or strained muscle? Her right side is her affected side, but it usually has high tone, not low. Any advice will help, I'm dreading taking her to the doctor because they think of me as a nervous parent and will most likely send us away with a quick "don't worry".