Apart from the fact that Fudo is right, women with large muscles are usually genetic freaks or androgen-built, there are some nice trap exercises that work the lower parts of the traps.
Inclince bench rows - Lie face down on an
incline bench (roughly 45-55 degrees) and grab a pair of moderatly heavy dumbells. Row until the dumbells reach the bench and hold for a one-count then lower slowly.
Prone trap raise - Again, lie face down on an incline bench. Grab some light dumbells and, with a slight bend in the elbow, raise them up and towards your head. Think a bent over
lateral raise but with the dumbells moving more towards the front.