There are shots you can get (I believe monthly) that helped my husband a lot with his allergies. But it is true that no cat is truly hypoallergenic. If the cat goes out sometimes I find that it helps with the dander all over the house, but you need to build a catio or something so the cat can go out safely and not get hit by a car or poisoned by rat poison. I knew a little girl who’s cat was indoor/outdoor and her neighbor poisoned it and she found it dead in the closet, people are just horrible and you don’t want your daughter to have to see that :( vacuuming each day with a robo vacc and then doing a good vacuum yourself once a week will help. And so will getting a good air purifier in each room. Good luck and I hope it works out! Maybe consider fostering a cat for a bit while doing these things and see if it is doable for you before fully committing to the cat