I think this is slightly inaccurate. For me, I didn't get the dialog with Curie until after I gave the cure to Dr. Forsythe. I gave him the cure, then talked to Curie before going to talk to Austin. Then I was able to send her to settlements as usual. With my first character I was never able to send her to a settlement.
I spent about three hours finding this workaround (before it was even on the Wiki page) and that's what I had to do. I tried initiating the dialog with her before handing over the cure, and just got the same passing comments she'd make prior to becoming available as a companion.
In any case, currently this is the only workaround for it that I'm aware of.