What to do when your mom hurt her back and is in bed?

You need to make your Mum as comfortable as possible. Have a bedside table where she can reach things without moving her back. A good bed tray can really help here. Get her a reacher so that she doesn't have to move if she needs to get something light within her reach.

She NEEDS to have an X-ray to make sure that she hasn't broken a bone or done any other back damage. (My Mum turned over in bed and she had 5 severe compression fractures in her back, some of which she got by being misdiagnosed as having a pulled muscle.)

Get her a modern bedpan, the kind with the very low section in order for you to slide it under her when she needs to use it. Do not let her get out of bed if at all possible. Make easily digestable meals like toast and scrambled eggs. You may want to get her a drink supplement like "Boost or Ensure.)

Ask and seek out information on how best to help her.