Liz Buchanan BVSc MRCVS
It sounds as though your kitten seems bright and well in herself. However, I don't know how long you've had her or her real age, so you might want to be aware of atresia ani, a condition in which cats cannot poo because their anus doesn't form. If this may be a possibility please see your vets as an emergency. However, it is not uncommon for healthy young kittens to sometimes struggle to poo without their Mums, and also quite common for the cats not to want to poo in an unfamiliar / stressful space (as gently as you do it, leaving your Mum at 7 weeks old is both unfamiliar and stressful).