You said she didn't cooperate, but you didn't explain what it was. Did she not return the documents in time or did she not take the initiative to check with you? If it is the former, you can let her go without delaying your work. After a long time, she will be anxious. A good cashier should give the bill to the accountant every day, so as to calm down. If she doesn't take the initiative to check with you, then you can summarize it and tell her the balance of cash and bank deposits. It is her responsibility not to pay the bill, and she has to bear the shortage of cash on hand.
But you should try to communicate with her to make the relationship more harmonious. After all, financial work is coordinated by two people. If she makes a mistake and your account is inaccurate, the boss will blame you.
By the way, you said you were new, so is it possible for the cashier to cheat strangers? In that case, you should get close to her. If you can't, tell your boss. No one wants someone who has no team spirit.
Remember: everything goes well with people.