Oh preggoeggo how incredibly awful, I am a dog owner and can't even begin to imagine the trauma your mum is going through.

Could she perhaps try asking the groomers nicely (I know that sounds difficult to do given the circumstances) if they will contribute towards the expenses? All I can think of is if she goes in with an angry approach then they will probably say no. Not sure, but maybe the groomers have insurance to protect themselves from any pet injuries that occur whilst the animal is in their care?