Diabetes is very rare in robos, you could try getting some diastix and ketone sticks and testing her urine. When I did this with Jam I put him in a tub till he had a wee which wasn't that exciting for him, but didn't take too long. I then just dipped the sticks.
It may be a kidney issue in which case the extra protein isn't actually so good as it overloads the kidneys forcing them to work harder at exactly the time they shouldn't be.
Hams can be completely different, Jam and The Cloud were brothers and couldn't have been at more opposite ends of the spectrum character and personality wise. The Cloud was hugely aggressive and completely untamable, but that was just him and I accepted him and loved him the way he was.
I have to say all my hams will eat poo at times, and they've all eaten sand too, hams are just different, and we have to accept that some of them they do things that we think are a bit gross, but to them it's completely normal.
I can't help with the standing and falling backwards as I've not had this before. If you feel her health is not as it should be, if she's showing signs of illness and struggling to do normal hamstery things, then it really is the best idea to take her to the vet
