I don't want to scare you, but high blood pressure is not good during pregnacy. The only thing they can do to bring her blood pressure down for good is to deliver the baby. They will probably monitor her for a couple of days and try and hold off as long as possible. I think they might be able to give your sister something to help bring her pressure down for a little while so the baby has some more time to grow. But they will most likely deliver the baby early. It will be the best thing for both of them. I'm sure eveything will work out, even if the baby is born early it should be just fine, there is a lot they can do for it and the baby has a really good chance also, especially since they are starting the steroid shots.
Thank you for the reassurance. I got a chance to talk to my sister yesterday. When she went in her BP was 200/130. As of last night it was 133/75. She'll have an ultrasound tomorrow. The doctors want to wait until 34 weeks to deliver but aren't too positive that my sister will be able to go another 5 weeks. She won't be leaving the hospital until the baby is born though, which is a relief to me because at least she'll be monitored constantly. I'm just relieved that for right now she's where she should be with her BP. She's still swollen but feels better than she did.