Joint Account- How are they considered for D/I Calculations?

[Rian Ash]

Hi BP Experts,

Here is the scenario I am exploring and would like your advice. 

My wife currently can't qualify to buy a property since she doesn't have enough in reserves. I have a brokerage account wherein the balance is enough to take care of the reserves requirements if that account can be considered. 

If I add her as a joint account holder to that account, will that be enough for the balances to be considered in her D/I calculations. If yes, will that happen immediately or we need to wait for 2 months statements showing her on the account?

Thanks!