I have seen some people who apparently apply again and get it, quite how often this happens I have no idea, I doubt it is that common but they only have the application fee at risk.
I remember entering the US and was asked how much I had on me, less than $20 in USD but like everyone else I had CCs.
Begs the question how many people visiting the US do not have Bank Accounts, must be very few.
How is a Bank Account proof of a tie?
Enough depends on their plans as mentioned above.
From a practical point of view I assume she is not in a position to increase her balance anyway, it is what it is.
Review the questions asked in the DS 160