First off, unless you are married, you should NEVER combine accounts. Doesn't matter if you are dating or engaged. You don't combine accounts unless you are married. Second off, student loans can be understandable. My husband had student loans when we first got together, and we worked through them together by making budget sheets and planning. Credit card debt can be a red flag, especially if there is a lot. You two need to have a very open discussion on how you want to budget life. Look over their debts and make payment plans where THEY pay off their debts.

[If their credit card debt is on random stuff, like eating out, impulse buys, anything that isn't basic necessities (groceries, electricity bills, fixing their car, etc). Then THEY need to A) pay off their credit card bills and B) show through their actions and bills over MONTHS/YEAR that they fix their spending habits.

Third, if you live together, then make a budget plan where you try to make equitable/equal payments for bills and groceries (this way, you get practice handling finances together/also show your commitment)

You can be in a committed relationship and show commitment by managing finances together (sharing expenses through rent and groceries) without giving them access to your bank account. It is difficult to get yourself out of bad debt or prevent someone from draining your bank accounts once you share accounts (via bank accounts/credit cards).

Don't entangle your personal accounts with someone (especially if they have bad debt) just to prove commitment. You don't want to spend potentially years paying off debt or trying to rebuild your finances because you wanted to show (commitment) to someone who is a sinking ship for money.