The over all impression is quite nice.

The main thing that sticks out to me as odd is that Heidi seems to be cross eyed. They also both seem far away with their thoughts and do not really interact with their facial expressions, but that may have been intended.

The other two things are minor.

Kat's arms (especially upper) seem to chubby for her other wise slender body shape (boobs not considered ). This may be since you usually draw "a bit more full figured" girls.

The lower part of Kat's pants fall strangely and seem to wide in the middle. of the leg. if they were skin tight this shape would be ok but as it is it looks odd to me - especially on her left leg. They seem to be neither bell-bottoms (too narrow at the foot end) nor relaxed cut too wide in the mittle of the calve.

Hmmm maybe still one more "negative" thing but thats nick picking I think. If the triangle on Heidi' hips is not a pocket but an inserted panel I would expect it to go a bit lower to where the zig-zack-ing of the seem ends since thats where the biggest part of her bum is. I also to not quite see why she would need it. Her belly seems to hang over her pants so they would not need to be so much wider a round the waist. But I could be wrong since I do not have any first hand experience with that.

The high lighting and shadowing look nice to me and I like the over all setting of the two - how Kat leans on Heidi's belly. Still a bit more facial interaction would have made it even better.