Here are a few things you may want to consider before you make up your mind on what to do:
Do you think that she knows that you are in love with her?
If not, how do you think that will effect your friendship with this women once she figures it out?
Do you want her to know?
(If you do not want her to know, than giving her an expensive gift and a some what lesser gift to the other girl will cause suspicion)
Are you prepared for what may come next if the bf knows of your feelings?
How long are you willing to put your feeling aside while lavishing her in gifts while sitting back and watching her date other men ?
Not trying to be mean just giving you some things to think about.
Love is an amazing and wonderful gift in and of itself. But if that love comes with a price meaning that she will never be yours. Than is it worth loving that person if it means to sacrifice yourself finding true Love.