As a wife, but one in control of the finances and a mustachian, I would say that I can understand a little.
Perhaps budget in an allowance to start with that she can spend on whatever she wants to, it may be a bit higher than what you would like it to be at first but it's also a great way for her to be able take stock of the value of the things she desires.
We also make smaller goals on the way to FI, more obtainable ones. Like when we paid off the mortgage we each had a gift in mind as a reward. It moght not work for everyone but DH and I were happy to forgoe many things to reach this point and then choose a special momento each.
We also have 1, 2, 3,5 etc year goals that we re evaluate each year. It's fun. Holidays, spending, donating, saving, investing; it's all there.
For us, paying the mortgage off was a huge mental jump for us but we are in Australia and cannot claim any interest back at all.
Good luck.