I think I managed to trim a nail. But not one that really needed it. She sat to lick the baby food with her back feet under her and her right side to me, when the long nail on her front paw is on the left. And she kept being suspicious of what I was up to, rather than being busy licking the food.
But afterwards, when she was in her cage and begging for treats she had both front paws on the bars and I was giving her small treats that she can pouch without using her hands. And I thought they were perfectly positioned for some clipping. It might involve doing too many things at once, but it's worth a try.
Although to complicate everything, I just noticed that she has one front tooth that's longer than the other. I need to get a better look and decide if the long one is too long. Because if that needs trimming the vets could do her nails at the same time.
I haven't noticed any change in her behaviour and her weight hasn't changed. But she is about a year and a half old, so maybe she's getting old without showing it.