Frustration (don't we all get it sometimes)

inmyownskin

We are at the half-way point (10 of 20 weeks) of a competition (Biggest Loser) at my workplace I have lost 8 lbs and some inches (dont know exact but my clothes fit better). It took me about 4 weeks to really get into it (exercising and eating healthier and less). I now exercise every morning - approx 20-45 mins depending on my time factor and burn approx 200-400 cals. I try to eat at the 1300-1500 cal range. Last 2 weeks I have GAINED a total of 1.5 lbs! My main frustration is the current "winning loser" started at the same weight as me and is taller (I am 5'3" she is 5'8") and she has already lost 20+ lbs and averages about 4lb loss per week!!! wtf?? What is the difference here?? Any help/advice is welcomed!
PS my only thought is I am pear shaped (carry it in hips and thighs) and she is apple shaped (more in the middle).
I have 5 weeks left in the contest and need to boost my losses! Thanks!