OK, I see what you were getting at (you can edit your own message to fix it).
Yes, colloquially you could use "right" for both An ea and Is ea IN THIS PARTICULAR EXAMPLE.
"She has a cat, right? Right".
But there are other situations where "right" would not be an appropriate translation for an ea or is ea. For example you can say feirmeoir is ea é for "he is a farmer".
And people do still say "isn't that so?" but I think I'd be more likely to say "She has a cat, doesn't she?" in a sentence like the one in this exercise.
Honestly, this sentence sounds weird. I would say an bhfuil would be better here than an ea and a good way to do an ea would be cat atá aici, an ea? i also feel nach is better than an for 'isn't it'. 'An ea', i feel, would be more like 'is it?' - she has a cat is it?
But without the use of the copula already there, using it makes it weird. No native (afaik) says Tá sé fuar, nach ea?, but Tá sé fuar, nach bhfuil?. Basically, you repeat the verb in queation.
Perhaps An Lon Dubh will see this and comment.
A similar conversation is possible:
Duine A: Tá cat aici.
Duine B: An ea? (= "Really/Is that so?", some dialects use "Nach ea?" instead.)
Duine A: 'Sea
However this exercise's sentence doesn't make much sense, the first person is basically saying "Really?" to themselves about their own statement!