slim, do not be afraid of heavy weights!! i had the best results with female clients hitting them hard on compounds in the 6-8rep range for 5wks and then lightening the load and hitting a 12-16rep range for 5wks and repeat.
i used standing dbell curls, dbell preachers, tri pushdown and underhand grip single hand tri extension (these would have been a constant 12rep range throughout heavy phase)