Hi there. This actually happened to my son a couple of times and once where he fell and hit his head on our stone counter on the way down and gave himself a black eye! We went to the doctor and they said he had orthostatic hypotension. Kind of that thing where you stand up too fast and get dizzy but amplified. For us, it had to do with blood sugar. His blood sugar was too low. It usually happened after it had been a long time since he ate as well as he was dehydrated. Could anything like that be going on?
https://www.mayoclinic.org/diseases-conditions/orthostatic-hypotension/diagnosis-treatment/drc-20352553 That's some information on it. We fixed it by making sure my son worked on hydration and ate at more regular intervals (especially when first waking up).
I like this article: https://www.health.harvard.edu/diseases-and-conditions/lightheaded-top-5-reasons-you-might-feel-woozy Low blood sugar and dehydration are on the list. With the age of your daughter, those can be likely reasons. The others, not so much. But take a look and see what you think.