IMO, if you and your DH are financially independent (as in, your parents aren't supporting you in any way), your finances are your business alone.
For example, I have a 22-yr-old son. I don't comment on his finances because he is very independent. If I were, say, sending him money every month and I found out he was buying cigs (he doesn't smoke, AFAIK) or partying every weekend, I'd speak my piece.
My late MIL was the queen of butt-inski. She'd make comments about how DH and I spent our money (we lived frugally, but she lived as if it were 1935!). There was no way to shut her down - or, DH refused to deal with it. I'm sorry you have to put up with this.