Help for My Mom (Injured Back)

So as the title says, I’m looking for some help for my mom. She just recently injured her back for the 2nd time in a year, on top of the fact that she spent 20 years in a grocery store (lifting, standing on hard surfaces, etc.). She is 57 years old, 4 foot 11, 132 pounds, and lives alone. She is in pretty decent health, except for the back injury of course, follows a decent diet with plenty of fruits and veggies, and prior to her 2nd injury, was doing 25 minutes of cardio 5 times a week, as well as lifting weights 3 times a week (following a routine i modified off of a few workouts I’ve used myself).

First injury was her piriformis muscle on the left side.
They did not give her much information on her second injury, but she feels as if its the opposite side (piriformis on her right side).
She has arthritis in her back in the L2 and L3 vertebrates. She also has spacing issues between the same vertebrates.

She hurts if she lays flat which interrupts her sleep.

She WILL not join a gym. She prefers to do her exercising at home. She WILL not do any leg exercises, her knees are pretty much shot to shit due to the grocery store. Laying on the floor is out of the question for now, as she has trouble getting up off the floor.

What she owns is an Elliptical, a small set of dumbbells (up to about 15 lbs.), and an ab lounger (like a curve shaped chair thing). She could possibly be willing to purchase anything necessary to help her, as long as it wasn’t a huge investment.

She currently works as a teacher’s aid at a nearby school district where she helps with the Special ED. She walks around school which doesn’t bother her much, unless she gets a bit worn down.

I’m trying to figure out a routine for her to get back into exercising, as well as stretching, but I’m not very experienced with injury rehab or anything of that sorts. She just started doing a little bit of cardio on her Elliptical this past week and is slowly building her time back up, as well as lifting weights for her arms.

If anyone has any ideas of exercises to do that would slowly help build her strength back up, as well as increase mobility or flexibility, that would be amazing. Thanks for help in advance…