Hey Jason 
I know that if it’s the same account, you can’t add it again but I’m not sure about the same bank, different account. If you message live chat we can look into this in more detail for you 
I may be confusing things, but I was just able to add my Wife’s Vanguard in as well, so now we have two Vanguard accounts in Emma. Woowoo!
If possible would you please add my bank/credit union PSECU - Pennsylvania State Employees Credit Union. Thank you