I wish I had the firmness you do, but literally anyone that asks me to ride, gets to. Ugh. All the neighbor kids? Yep. (Fortunately they are all on the leadline).
Friends? Mostly. Which I'm fine with as long as they listen to my constant, "move your hands with him, move your body, relax, sit up straight, relax, relax, RELAX!"
Boyfriends? I've tried, but it won't ever work. They don't listen to my constant nit picking, so they have lost their oppurtunity. Heck, one wouldn't listen to me, and ended up having my horse bolt (that never bolts) and take off with him around the arena..multiple times..at a gallop...
I decide now by if they are willing to listen and learn, I will allow them to ride. Now if they act like they know everything, and think all you have to do is pull to steer, pull to stop and kick to go, nope. One case I had my cousins friend come over who bothered me for 2 hours to ride, and eventually I caved in. He said he had ridden before, bragging how good he was... I got sick of listening to it and told him to get on.. No less than 2 minutes later, my horse was trotting with his nose in the air, taking advantage of him. Hmm, I thought you knew how to ride? Huh.
I personally would say no to her too.