The USTA has stated explicitly that they do not require the best players to play on lines above weaker players. The only exception to this policy happens in 4.5+ or 5.0 + leagues where it is clear that the player in question is higher rated.
By not requiring the best players to play the top lines the USTA avoids having to deal with complaints of lineup stacking.
I am sure that the other team knew they would only be winning 1 singles court so they took the sure thing and played their best player at line 2. In absence of a stacking rule this is good planning by the other captain. BY doing this periodically she places doubt in the minds of her future opponents where this star 3.0 woman will be lined up.
"You should be playing linebacker, not singles."