Asklemmy

In recent days we have been giving home to a black kitten less than a month old yet to be named, the thing is that we already have a cat at home. My cat "Rubia" has been with us for 13 years now, beyond having lost her eyesight due to age, she is very healthy. But since the new kitty arrived I have seen her very stressed. She can't smell or hear the new kitten without snorting, she eats very little and hasn't gone to the bathroom for a couple of days. I've seen videos on YouTube and read several articles where they say this is normal, but I can't help but worry. I'm worried that forcing her to accept a new cat will affect her health at the age she is, but I also don't want to just abandon the new kitten, although if it turns out that things aren't going to improve, I would be forced to look for someone who can adopt her....

Update: Thank you all so much for your advice, I will do my best to follow them 💜. Recently Rubia has returned to use her litter box normally, and although she still doesn't like Morena (tentative name of the new kitten), I feel more optimistic, we just have to take things slowly.