Ok, this is interesting, I just got the email to activate the account they set up for me but I already have a mileage plan account. Let's see how I can milk this
Similar to your situation, but I followed through the link that said:
"Already a Mileage Plan member?No need to activate a new Mileage Plan account if you already have one. Just let us know your existing account number here. We'll automatically deposit 10,000 bonus miles in your account.".
Just waiting for mileage to show even though further down in the email it says:
"Choice of 10,000 bonus miles or $100 discount is valid only for active members of Virgin America Elevate as of December 5, 2016 who were not members of Alaska Mileage Plan.".
I'll keep you guys updated.