@Eva,
Now that youve got a "Jenny" on your hands, I asked my Amish neighbor why he has only Jack mules in his team. "They are easier to geld" sez he.
Elam (the sone of my AMish neighbor and a new farmer himself) stated that all mules gotta be gelded so they dont get aggressive. He says that "jenny's" or "hinny's" (dads a horse and moms a donkey) are less agressive than jacks (male mule or hinny), but not completely. They may be sterile but they get :frisky" and this can translate into aggressive behavior.
Elam said that when they breed a mule or a hinny (I think hinny may just be a Pa German word ), they always sell the ones they breed because if they are there with the parent and grow up ungelded, they get really aggressive (kinda like Amish teenagers in "rumspringeh").
I think Id conasult asomeone with mulish expwereience and get their opinion about what you may be in for. We have a stock auction in Vintage (a small town near us), and they often sell young mules at auction and the AMish always seem to be "trading" the ones they breed for ones that someone else has bred . They can be really big (think about a percheron or a belgian mule. THEY ARE MONSTERS .
So, gelding is probably a good idea and maybe think about selling her to someone who is a mule fan or is AMish. (You have horse auctions in your area no?)