She is beautiful. I assume you will have someone with you. From what I gather a lot of people say the puppy is more secure emotionally on someone's lap and may then go to sleep. If you have a long journey you may need a toilet break so could take a puppy pad with you. Have some wipes and kitchen roll in case she is sick, and an old towel or blanket to cuddle her in. Make sure she has a collar on with an identity tag with your number and possible a short lead to restrain her if necessary.
I would take a list of everything you will need to pick up with her e.g. vaccination certificates, parents health check papers, a sample of food that she is on (and feeding guidelines) worming and de-fleaing advice, a blanket that smells of Mum and litter mates etc etc.
Re leaving the mother, she will be weaned anyway, and it will be the natural time to leave Mum, who may not be over interested in her any more once she is weaned. When I got my last puppy I put him to his mother's face to 'give her a kiss'. It made me feel so sad but I still remember that moment as one to treasure and the dogs didn't seem bothered in the slightest!
