Katyj, what is the purpose (if any) of the transfer? Will she be properly assessed there? It could be a positive move for her as there are specialist nurses, physiotherapists etc. in rehabilitation wards. Don't take the 'one day' as certain either. Doctors there may well want to do their own checks.
I'm assuming that she's had a needs assessment and there are proper arrangements in place for her return home. If not, that's next.
On past experience, I'd double check everything as it seems that communications often break down. Don't assume that things will run smoothly.
Will carers be available immediately when she's discharged? Is her GP informed? Does everybody have a copy of her care plan? Do they all have contact details for each other and you?
Do make enquiries about the times of care visits too. Things can go wrong:
My elderly neighbour, Frank, was sent home from hospital and nobody turned up to care on the first day.
His son lived abroad so he had to hit the party wall (with his walking stick) for quite some time to alert the lady next door to his plight.
He was weak, hungry and thirsty, but, apparently, everything was in place - for the following day!
(We kept an eye on him after that, of course.)
Still, all was not 'ideal'. Carers would come at 9.30am (when kids were at school) to get him up, dressed and fed. (We took him tea and toast at 7am.)
They'd put him to bed at 6pm (then home to their own families) He had a TV, drinks and pee bottle, thank Heavens - but a short day and long night!
One day, returning from school (so about 4pm) I could hear him shouting and cursing. The carer had left at about 10.30 am - but failed to leave his walking stick within reach - so he was stranded in his chair, desperate for a drink and the loo!