Tessa and Mariah's fanbase only really hit full flow recently, AFAIC. They'll survive. Y&R can do whatever it wants, it chooses not to here for ulterior motive, as it has for a couple years now.
As a gay fan I'll say, as I've said before, that I think the entire, shitty purpose of pairing Mariah with a tertiary, unpopular (for most of her run, anyway) woman in the first place was to section Camryn Grimes off from any leading frontburner story with men the show and/or network had earmarked for female leads they found more conventionally desirable. They think she's too ordinary for Kyle or Devon but it's fine to throw this chick at her. Ugly to say, but I absolutely think that's the toxic mindset and we've seen it before in daytime with lots of str8 characters. And in doing it this way they were able to claim it was progressive and forward-thinking.
There's nothing wrong with Mariah being bi, and you can play drama with her and Tessa or any number of other more interesting women in the future. You can do it right now with her and any woman, not just men, and take time away from Abby or Victoria! But AFAIC they want to keep her where she is to keep her away from leading story with the rest of the show. That is an admittedly ugly perspective. Sadly, as a gay viewer who has seen this happen both with gay characters and with attractive leads of any orientation who do not fit into a proscribed box, I also think it is 100% the truth.