How many calories a day should I consume while dieting?

I am not breastfeeding anymore and I want to lose the last 7 pounds. My trainer says that I should be working out 6 days a week and eating 1300 calories a day. I am 5 foot 9 and 135 pounds. I was 125 pre-prego. I have a small frame. So, I am wondering if that sounds about right. Some days I am fine with the 1300 calories, but today I am starving and have already eaten 1200 calories, and I haven't even had dinner.

I am eating well and working out 5 days a week. I do 4 days of really intense cardio/weight training and then the 5th day I usually do something I like (walking, swimming, etc). Should I be consuming more or does 1300 calories sound about right? Is it normal to be more hungry one day than the other? Any advice would be appreciated!