Hi J., my twins didn't sleep through the night until almost 1 year old. When I was concerned I went on the internet and looked up some info about this. What I learned is that only around 50% of babies sleep through the night prior to their 1st birthday, most of the rest start sleeping through the night around 1 year. I nursed my girls and was up quite a bit the first 6 months.
I did have a friend who let her babies sleep in bouncy seats, they were just much happier there. I don't see what would be the problem with that. You may also want to check out the reflux, as it may be that she is having this and that's why it is uncomfortable for her to lie flat. As far as just sleeping through the night, you may just have to be patient until she is able to sleep for longer patterns at a time. Some do this early, some take longer. Although it is hard for mom's and dad's, there is really nothing wrong with the latter. Best of luck! F.