Maybe it’s hindsight seeing Worf in her position for all those years, but between the two of them, one of them would go eventually. They essentially played the same character; rough, kick ass, etc… Except one came with a Klingon backstory and one came with a tragic rape-planet backstory.
I don’t think (other than fucking data), there’s a single plot that they could give to Yar that they couldn’t also believably give to Worf from an emotional story perspective. They’re essentially the same character.
Easy, baby daddy show up and drops off kid, add rape trauma or scifi mind wipe If you are squeemish. Also, and this is important, the father had a sex change operation and was the raped herself. Now she advocates for all rapists being raped since it worked on her. The crew debates whether they should stop the raping because it’s internal policing.