I’ve been married for 32 years and we were together for 7 years before that.
Everyone manages their finances differently, but the common success story is to always remember that it it is an equal partnership. Neither does anything regarding finances without informing the other and discussing it first.
If you don’t do that, it isn’t a partnership.
Relationships begin with respect with results in trust, and it takes both of those to keep it going.
Failing to discuss something like this with your partner before doing it shows a lack of respect, and it’s no surprise that the result is diminished trust.
Do you want a partner you can respect and trust or not?
You get what you give.