Does it mount to the floor or to the couch, that will be the defining factor, if you ask me.

You could have SIL put blocks under the feet to elevate it to a better height for you. I did that on all my dad's primary furniture after his hip replacement and it worked perfectly. In fact, he asked to leave them even afterward because it was so much easier for him. (I made new, better-looking ones and stained them to match, he never noticed it, but I did. )