My best friend gave birth 1 month after me and she has already lost all the pregnancy weight, whereas I still have 5kg left to go. She looks great and seems to be handling motherhood better than me overall. I am happy for her, but also a little resentful. Is this normal?

I think you shouldn't compare yourself with your friend. It's not healthy for your self esteem neither will it be any good for your friendship with her. Motherhood, who loses weight first, who's a better mommy -- none of this is a competition. The teensy feeling of resentment while normal (who doesn't get jealous every now and then) can be channeled into reaching your goals such as losing that extra 5kg. Everyone goes through pregnancy and post pregnancy differently, just focus on yourself :)