You can try to use her account but usually both names have to be on the account. If the bank rejects the deposit the IRS will mail you a check. Ask the bank if they will accept the deposit or add your name to the account.
The direct deposit will have both names on it. Some banks will accept it in an account in only one name, and some banks won't. Some banks don't even check the name. They are not required to, but the IRS encourages them to check. You can ask the bank, but the people at the branch or on the phone might not know the technical details of how direct deposits are processed.
If you get a check instead of direct deposit, the check will be payable to both of you (John AND Mary, not OR).
The deposit will have both names, but probably only one SSN; the name of the "first" spouse (the person on the top line of a printed return).
If you are the spouse named at the top, you would have to check with your bank to see if they will accept a deposit into your spouse's account. It's up to the bank--the IRS encourages banks to match names and SSNs but the bank can do whatever it wants.