She might be waking from the cot maybe being a lil small for her and banging into it when moving in her sleep.
We bought DS1 a guard rail to make him feel 'secure'. We didnt need to use it for long. You can get them at baby stores, big w, kmart, target etc.
We also made a huge deal about how exciting it was when his bed arrived. He helped his dad put it all together and helped me make the bed.
Cant remember much more. He has been in his bed for nearly a year now. He got too big for his cot a long time ago
I also think I was more worried than he was! LOL...
Good luck - I am sure she will be fine