Same here. No matter how much I insisted (but still being polite) she said she was unable to apply the $30 discount because that is for new lines.
I'll have to try it later and hopefully I should be able to get it either way ... I ordered a phone and my soon-to-be wife ordered a phone (we each currently have individual accounts) and both phones were on my Credit Card. Evidently, when we go to activate and join one family plan it is the same as "activating a new line" so I am hoping it should work for that to at least cover the activation fee that Verizon wants to charge