“There are no female aliens in our game because we don’t know how to make a female version of this alien” You know that alien you just designed? That male alien? Give it a female voice actor and have characters refer to it as she. That’s it. That’s literally all you have to do
Make her shorter if you must
Make her BIGGER if you aren’t a coward
Take your male alien bodytype, make her like 4 feet taller, give her an extra set of arms and sharper teeth, and as muscular as shit.