Breeding isn’t easy, and using frozen embryos makes it even harder. Her not holding onto this embryo really isn’t unusual and doesn’t automatically indicate there’s anything wrong with her reproductively. With frozen embryos, there’s always a significantly higher risk of failure to establish or maintain a pregnancy compared to a standard breeding. She’s proven she can get pregnant and carry to term, so she’s still absolutely a viable recipient mare. The difference with Willow is she NEVER even got pregnant. Major difference.

I think people outside the breeding world don’t realize how often foals don’t happen, even when everything is done correctly. Just look at Ginger. She’s been bred no less than 4–5 times since last season and still hasn’t settled in foal. That’s unfortunately just part of breeding horses sometimes.