What about the name Daisy?
6 weeks is not only too young to be away from mum, but too youung to be left all day too. She really shouldn't be at your mums alone- bring her home where she will have company!
I would bring her home, and make a room just for her- spare bedroom /even the bathroom if there is no loo in there, or make sure you close loo lid at all times. You can keep her bed in there, water bowl, some dry food, and toys.
Put a ticking small clock (£1 shop travel clock is ideal) under the blanket in her bed and it is like mums heartbeat. Also when she is in this room, a portable radio on quiet set to radio 4 (speech mostly) keeps her company. I like to put a small cuddly teddy in there too.
You can get Frontline for fleas from online or Pets At Home, but you can't use it untl she is 8 weeks onle and 1 Kg in weight.
Now I would personally only keep her in this room at night, and when she needs peace from dd during the day for SHORT periods. Like a bolt hole for her. So she can sleep, kittens need lots of UNDISTURBED sleep!
When she is bigger and more robust she will be able to get away from your dd herself, or scratch and hiss to let her know 'no' !
Oh and when she is older and bigger and can jump to high places, you should make her a bed on a high surface like a window sill/bookcase/cupboard where she can go to rest but your dd can't reach her. She won't be able to jump high yet so thta is why I suggest the room just for her.