Originally Posted by
xliioper
DL Reserve has Sky Club access on both DL metal and DL marketed flights. Vanilla Plat only gets access when flying DL metal (with lone exception of DL marketed WS flights).
On the other hand, Amex PLT can access the centurion lounge flying any airline but the DL Reserve can only access it when flying DL marketed flights.
So it all depends on her flying patterns.