I wrote the answer late last night and I realize it's gliberish !
I should have written : Try to see the captain, she'll say a word for you
Sorry, this game really doesn't need any added difficulties ;-)
I'm thinking the the whole Rachel Helping Hand is bugged. As even when you have the doc helping you out, you still get the same text of Rachel telling you that the Doc should have a fix. No shit, been going to her for week, done that.
I get the 'try the girls to help out' speech from teh captain, but nothing changes.
As the text sequence doesn't make sense (the doc thing), thinking there's a bug in there that makes it much harder to get to than it should. Other events blocking etc.
And a thought, when the walkthrough says 'unlocked Lindas Help', does it mean just started and in progress, or finished with all the stars filled? Because all the wording and hints can be misleading. As in the 'visit me before lunch' you'd take as anytime before lunch. But no, it actually means the exact hour before lunch. 11am and only 11am.
EDIT: Bugged, or just coded to be really specific, bit like the above lunch thing and poorly worded.
With the Doc, go through the days as shes thinking about the cure. On the day she decides to do it AND gives you the treatment for the FIRST time, then you go and see the captain right after. You'll get the 'I can tell you anything' line.
Before that event with the doc doesn't do anything, and after you get the broken talk about doing your sisters you had before from the captain. So it's another 'one shot' trigger as far as I can tell.