Red-legged Partridge do sometimes (as you say) build two nests, lay a clutch in each, and then the male and female take care of each brood simultaneously and independently. Perhaps she rejected "his" nest more, hence throwing those chicks around.
This is really sad isn't it. She was clearly so distressed, and perhaps she's just going through the motions now.
As the Red-Legged variety were introduced for shooting, there must be lots of partnerless birds after the season, so maybe they do subsequently pair up again with another mate. I hope so! Have to wait until the new year to see - in the meantime, she seems to enjoy being looked after and kept amused.
I also live out in the sticks and have resident partridges and pheasants. Their tameness doesn't seem to stop them going "back to the wild" for weeks/months at a time.
It would be interesting to hear the outcome of this anyway :-)