As an NHS nurse manager I speak for myself, I would give verbal information to your mum from her notes, this all sounds very strange, I would go to through her prescription chart and tell her if an incident form had been completed. If results are straight forward generally a nurse can tell the patients.
As said up thread your mum can do a SAR now to access her notes but it's unlikely she will see them before discharge, there is a time frame they have to work to, to allow your mum to see her notes. Most trusts do not charge for this service now.
Did your mum fall? The trust does have a duty of candour to the patients when harm has occurred, this includes an apology and explanation of what has happened, how it will be prevented again and what your mum can expect now.
If I were you I would firstly advise your mum to ask to speak to the ward manager, failing that the matron for that area, failing that PALS. This will not affect your mum's care, she has a right to all of this information. You can of course take this on with your mum's consent, you say your mum has capacity, might be worth her writing down that she gives you permission.
I hope your mum gets some answers, this is not acceptable.