The stud fee may be the cheapest part of the whole thing...
You say you've been doing your research, so I am sure you know this, but there is a
huge difference between breeding cows and breeding horses; the only real similarity is the size of the animal.
When I first "discovered" miniature horses, I thought I wanted to breed them. Then I stumbled into the Mare Stare forum, and spent a couple of seasons as a fly on the wall, watching horses inhale hay for days or even weeks in anticipation of a few minutes of sheer drama. I saw so many foalings go horribly wrong, I decided I really didn't want to do that after all (in fact, I bought my oversized mini Syd because I had known her from a foal, and when she came up for sale as a 2-year-old, I couldn't bear the thought of someone pushing her out into a pasture with a stud to risk her life for $200 foals). Granted, a lot of the bad ones were minis, which due to their size have more problems than average, but the very first mare I "stared at" was an appendix QH with the barn name of Grace that died a week after foaling of a displacement colic. Grace was only 7 or 8, this was her 3rd foal; the others had been colts and her owner had been thrilled to have a filly. She nearly lost the filly, though; some foals adapt readily to being bottle fed but this was one that didn't. After a couple of other attempts that didn't work out, the owner was put in touch with someone who owned a mare that had lost a foal and wasn't adjusting to the loss at all (interestingly, the mare had been bred to the same stallion, so the lost foal and this filly were half-siblings). Miraculously, the two took to each other immediately, and the foster raised her to weaning age with no further issues. The filly was registered as "See the Grace in Me" after her mom, of whom she was the spitting image . . . .
Good Lord, was all that really 11 years ago??! Doesn't time fly?
She's your horse, it's your decision. It's quite possible that breeding her may turn out to be something you regret, but then,
not breeding her may be something you regret, too. Either way, I wish you well.