I would not kid around with that. I would get a shower with no apron and a linear drain. add a shower bench, and no broken bones for dear mama

You are going to need to do some construction - change the location of the plumbing and find out if mom really wants a tub bath anymore at all before you do. If so - steps all around, plumbing at one end, handrail discretely installed along one wall where steps go to wall - handrail over that end of tub too.

I agree to change it to a shower. Add a hand held shower head and a seat, maybe even some grab bars if she needs assistance standing. It would be the best option for an elderly person who it getting limited on mobility.

Changing to a shower is the safest bet, is there not a shower somewhere else in the house that she could use?

i know I would cringe at the though of a 90 year old getting into a tub like that.

Sorry, but the tub needs to be removed and have one of those step in tub or shower with a bench and a grip handle . You will need something like this , regardless of what you use always be present when she bathes ,.

Handicap-Accessible Bathroom Waldorf · More Info

31 x 40 Soaking Walk-In Bathtub, - Soaker Tub, Right Drain Configuration · More Info

I think the step-in soaker tub would be ideal, as bathing takes less energy than showering, and is a place of respite that is good for the soul. If you could change the location of the faucet, perhaps then you could purchase a seat that attaches to the tub and swivels her 180 degrees? I know assistive devices exist for easy chairs, to help the person get up, and am just inferring what might (and Should) exist.