It depends on a lot of factors, such as how hard the wearer is on her rings, what sort of routine and if it will be an everyday or special occasion piece. Personally, I wouldn''t do it for an everyday ring, since zircon is brittle and easily abraded.
By the way, have you asked for a handshot of that stone? I think that there is a very bright light shining on that gem and that, in real life, it will be too dark. The setting is very lovely.
Don't get that stone, it will look like a very dark dark red garnet. In fact, if you want a more durable stone in that color, then get a dark red garnet. I find that color rather masculine if you ask me.
ETA: Does she like soft feminine color? If so, this is a pretty pink and very affordable.