Have you asked her why?
I started to learn to fly after I got divorced. Had I started when I was still with the ex, she would have definitely been resentful of me having fun (I had had loads of unpleasant examples of that already from her, but being much younger I accepted that as being normal female behaviour, whereas today in the same situation I would have legged it instantly - though a marriage and kids will make that much harder) and while I can only guess how it might have been resolved, it would have probably involved spending an equal amount of money on something for her to do.
However, we had small children then and if we were going to do something together (but without the kids) the kids would have had to be with a nanny, but the ex bitterly resented the prospect of a "stranger" messing with "her" kids. Result: a deadlock where neither parent is able to have any fun
I think many relationships have an underlying dynamic which tries to prevent either person doing anything. So the man escapes down the pub; the pub across the road from here has its bar propped up by the same ~ 5 men every night, and most of them are married with kids.