I feel your pain. I've been fortunate that I've been able to hold on to my "first foal" from this 2nd chance with horses for the last 22 years. He was foaled when I stepped into to get another cup of coffee, one cold night on April 4, 1991. I've been able to see 26 of his 27 foals the morning of their birth, actually got to watch one being born........sneaky mares! Haven't had a foal around for about 5 years but he may be a dad next year, the mare we picked up about 2 months ago went into heat twice and that's all she wrote. First time she's been bred and she's 10 years old, but the 2 of them are peas in a pod! They don't know they're horses, will follow you around the acreage, put their head in your chest to get their ears scratched, and come hauling a$$ when you whistle for them, sliding stop not more than 3 feet in front of you!
My BF of 9 years knows very little about horses, but feeds them in the morning. He's been lucky because we only had one mare, who was a rescue, that was really a snot. Kicked a feed bucket out of his hand and knocked him over! I have a rule about all the animals playing "well with others" and if they don't fit in, the get re-homed. She went back to the rescue after 4 years. Too dangerous for my BF, who has slow reflexes from PTSD meds.
I hope your filly has a wonderful new home and the new owners treat her well! It's always tough to see one go. :hug: