"Novella" doesn't have a standard word count across publishers. Each of them defines the word count for a novella, a novel, etc., usually somewhere on their website. And yes, Karen is right.
In the romance genre, at least, the stories as stand-alones or as part of a series range from under 10K to 200K or even longer.
So write your story and end it where it makes sense to end it.
Unless a publisher states a specific word count range for a submission you're targeting to them, it's usually not a good idea to try to force a story into a word count. I've done that for submissions to anthologies before, and sometimes it works, but other times the story is a disaster.