The key here is the landlord was not sure if you would/could pay

She doesn't know you. She needs to do her due diligence. Did you show her any proof of income or bank statement etc. If you go to apply for an apartment, people will ask about your income, run background check etc. And for urgent move-in, it should be understandable that the landlord is taking the risk that the deposit money may never arrive. It would be better that you simply gave her cash for the deposit.