First, she certainly could be bred by her son, so we'll have to watch her to see how she is moving forward. Breeding mother to son, or father to daughter is done by some breeding farms to "cement" some trait they like into the line. I'm not a fan, but she should be fine, as well as the foal, if it materializes.
Did you also get Clancy? I know if you did, you separated them, which is what should have been done, for sure.
She's a pretty girl! That Willow has produced some beautiful babies!!