PimsGarden
Songster
This is a great theory is test before anything else!There is an alternative explanation for the behaviour that you may want to consider. The old hen may be ill and the welsummer may perceive it as a threat to herself/ the flock.
the weight loss may be because she is ill, rather than because
You can test this by separating her and seeing how much she eats when not threatened. She should be ravenous if it was just the welsummer keeping her from food. If she just nibbles or pretends to eat, she's ill.
this also may be because she is ill.