There are particular low fat cheeses that can't be used as a HEA and feta is one of them unfortunately. You can only have full fat feta as a HEA but the low fat one can be used as a HEB if you are on a green day.
Halloumi is the same - 35g full fat as a HEA, 45g reduced fat but only as a HEB and only on the green plan
It's another reason why I love the green plan