They can't outweigh each other, otherwise you get versions of the utility monster problem.
https://en.wikipedia.org/wiki/Utility_monsterIf person A doesn't want to have sex with person B and person B would be inordinately happy to have sex with person A, just about all ethical systems would say they shouldn't have sex.
If person A has money in savings and is clinically depressed and person B wants to take that money and go on a vacation that would make them very happy, just about all ethical systems would say, no, that's stealing.
One of the things functional societies do is to limit the amount that certain people can make themselves happy as a mechanism of limiting the amount to which other people get hurt. Banning workplace relationships because of their serious potential for hurt seems like a straightforward case of this.