Seriously,
If that gun fit her, and she shot well with it, I would call the range and see what kind of deal could be struck.
Keep in mind, that gun is used, and may not have the maintenance a private individual would give one.
Self Esteem is running real high with your wife right now. This is real important.
Gun fit, correct basics and self esteem go a long way in keeping her interested.
The other thing is, sounds stupid, but you are married and understand this.
You listened to her.
Not "heard" her.
"Listened" to what she likes and this means a lot to her.
For your budget, no, I cannot think of any other guns other than used Rem 1100s, Beretta 303/390/391, Win 1400.
You are not going to find a O/U for this price range.
Being honest, the 20 gauge semi is a great gun - it truly is one of the best kept secrets.
I would double check gun fit, try to get that gun, or one like it.
Make sure she shoots another gun (one like it) , as even among same guns, there are little differences, heck it might be the grain of the wood, who knows.
I understand the Money and Budget, I really do.
One cannot put a monetary value on all this gun means to her now, and in the future.
As she progresses, this gun will assist another new shooter, it may be a family member, son or daughter, maybe a SIL, DIL, coworker for either of you, or somebody new at the range and "would like to try and shoot MY gun for fit?"
You will be standing 3 feet off the ground, with a puffed chest and grinning like an idiot.
Which is fine, you are supposed to.