Ipster, don't blame the opposing captain, blame the USTA.
They specifically mention in several places that the line/court assignments have no meaning and do not correlate to strength.
And then of course they contradict themselves also! (By mandating that defaults be taken from the bottom up, and by requiring that higher rated players in the new '+' leagues play at line 1.)
At any rate, there is no captain's code of honor that requires lineups to be set in order of strength. Some captains stack, some don't. If anything, take it as a compliment that the opposing captain did not want to risk her top singles player in a match against you.
BTW I am sympathic to your situation. I get ****ed off when I have to play against people playing up - waste of all our time and money. I personally would prefer it if playing up were not allowed, but I know I am in the minority.