Having her with anyone other than the MC of this story makes this story sort of trash, whether it be the MC of your other game (who would probably end up with Emi's mom, so there's the alternate prize for him instead of Emi) or any other random dude.
Yeah Emi is great, but what made her great was the story and the connection to the MC in this short story. Have her banging some other dude in another short story and you pretty much ruin what you've built of her character in this one. Hell she had years to get laid in college but didn't, that's a pretty solid character description to show she's will to work for what she wants and also avoid distractions and temptations along the way.
Alternately, and I know this would likely piss off the "OMG the LI of the game blinked at someone else (be they male or female), the game is trash, blah blah blash".. Well some of us can tell the difference between emotional cheating and someone just having fun, and we're not scared of intimidated by a woman having a relationship or sex with another woman. Hell we even like it. It's MUCH better than some random cock being added to the picture, there are way too many stories like that on here already.
So, alternate with Emi, the MC here, and maybe Becky and them develop some fun, sexy times, would be fun too and allow more story interactions.