I don't know about Decapitator's suggestion, but one thing that will work is to start a new campaign, and talk to her in that one. This achievement doesn't track that you're doing all of the bits in the same campaign, so you'll be fine. (Make sure to save your current game first)
You only need to do 4 missions before she shows up to talk to, which should be really quick on casual.
(I needed to do this because I did her plot-line while achievements were down last week - it works)
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