There’s a few nice 5 star hotels in Costa Adeje in Tenerife. We went to one in the new year and the area was lovely but ours was quite far up the hill, so wouldn’t be ideal for your mum. I recall some lovely looking ones further down which you should be able to find with a search.
Our favourite area in the Canaries is Meloneras in Gran Canaria. Quieter but lovely. There’s half a dozen 5 star hotels and they are all lovely (patek and Rolex shops :-) ). The beach there isn’t very big but it’s only 5 minutes walk from the huge beach at Maspalomas. High end shopping and restaurants. Casino. We’ve stayed at the Rui before which is right on the front and half board. Fantastic food. Also the Lopesan Baobob, which was great but set back slightly. We’re actually going back for the 3rd time soon and staying in another Rui literally next door to the other one, as it has more things to do for our daughter.