How do I adjust my child's bike shown in this video to improve fit and comfort?
Seat is too low. Problem with kids bikes as they have disproportinaly long cranks (Shes probably half your height, her legs are half the length of yours, yet he cranks are probably 145 vs your 175..... ). It works because kids are disproprtionaly flexible. I would probably try to raise the seat - just 5mm to start with... Thats much easier for me to say than you to do.   

From experiance with my boys, you need to get to the point she will ride the bike. Don't worry about fit, its not important for it to be 'correct'. If shes over trying different settings, don't force it on her. Ask her what she wants, put it there and get her riding.  If shes over trying new fit, and uncomfortable, give it a few weeks with no pressure.  Make sure the rides are short, if she is uncomfortable and you head out on long rides, it will put her off. 

As time goes on, you can suggest imporvements to try. if she does not like it (If shes like my boys, she won;t out of spite), put it back... 

The goal here is simple - just keep her riding...