Our fruits and nuts presenter told us that the Stone Fruits such as nectarines, peaches, plums, apricot, and cherries are the same species as almonds!
Peaches are Prunus persica and the almonds are Prunus amygdalus. Since they are the same species, they are graft compatible!
Your daughter is right! The almonds grafts died back to the peach root stock.
Good to know, thanks!
Wait wait wait. We Parents are the ones that told her that the root stock may have been peach.
She just called and told us that her almonds were now peaches, and she wondered if the peach trees in the back yard could have crossed with the almonds in the front to get peaches instead of almonds.
Hubby had the knowledge. I was guessing, because my wild lime tried to take over the lemon tree the first winter.