I told her to talk to her bosses about this because yeah, pretty much my store's fault here. We'll see what happens; she took the more recent expired product back and left the August stock for later. Kind of shitty because I was getting along pretty well with her and this probably poisoned the well.
We had a similar thing happen with Frito-Lay a couple months ago, only it was ~8 cases of chips that had come on a GM truck as cross product (or whatever the term is) for a Superbowl. All over a year old and the vendor didn't touch any of that, said it was ours to deal with.
Backroom TL's response when I called him over about this? Pretty much "maybe we should teach vendors to use a MyDevice or PDA and check the backroom themselves." Because teaching our rotating crew of backroom TMs and random TMs drafted help out the backroom would be too hard I guess.