This is really interesting. In my view there are 3 options:
1. Your purchase history isn't quite strong enough yet for her to offer you a very desirable bag so she's trying to manage your expectations in a very polite way
2. She's aware of other clients who've already requested the exact same bag, but have been waiting for longer / have a longer relationship with the store / have a stronger purchase history. All it takes is a couple clients like that and they'd need to receive 3 of this exact bag within a year to be able to offer it to you within a year
3. It may also be the case that she's been unable to offer this bag to her clients for 2y because they've been offered by other SAs and that's what she means when she says she hasn't seen this combo in 2y...
Just guesses of course!
Either way, I'd suggest to be a bit flexible on 1 element, e.g. the leather type, the size or the hardware... But please keep us posted and I hope it will happen soon