Hi there @Nicky1Holly
Thank you so much for your post and welcome to the community forums, it's great to have you here.
I am so sorry to hear that your Mum's landline is down! Can I check, does she have a dial tone at all?
Can I also ask if the phone is connected at a master socket or an extension socket? Also are there any other pieces of equipment connected at this point?
Has she been able to try another handset on this line at all?