Reply #41: Of course allergies are a serious concern, but that's not what the OP is talking about.

[The Velveteen Ocelot]

If your SO has such severe allergies that the pet is making them sick, obviously that has to be dealt with; and maybe the pet will have to go to a new home for the sake of the SO's health. But I don't think that's what the OP was getting at. Where a person wants to get rid of the pet just because they don't like it, or to control or even spite their SO -- well, that's a whole different story. Personally, I wouldn't get involved in the first place with someone who didn't like my cats; but if that did happen and I got the "cats or me" ultimatum, it would be strong evidence that the person was someone I didn't want to be in a relationship with. The cats would win, paws down.