You would have to prove that it was done fraudulently.
Does your mother own any share at all now?
If she Di reclaim the property the local authority would no doubt charge her share to cover the care fees.
Legal aid is not widely available. If you ring round /Google you may find a firm which can assist. It will depend on the case and financial circumstances to establish whether you mother is eligible or not. You may also find a local solicitor who may give you and your mother a 30 min/60 min free of charge consultation.
Do you have any documentation to evidence this. You will need to establish what happened.
Law firms hold their files for around 6 years now but the firm that acted on your father's death may still hold the file but you will only be able to obtain the file if your mother was the client.
The law firm may have had a duty towards your mother and may have been negligent. You could discuss this with the legal ombudsman.
I hope this helps. Do you have any further queries. Happy to assist if I can.