Six weeks old, she should still be eating from her mother. Get some of the puppy type milk from the Pet store. You can also get something called Nutra-cal this will supplement what she's not eating; it's in a tube and you squeeze about a table spoon out for her to eat. Another option is getting soft food, while vets don't recommend a complete diet of soft food, it's more appealing to maltese, at least until she starts to get the desire to eat. My maltese is 4 months old and it took him a few days to eat when I first brought him into my home at 8 weeks. My Maltese's sister died at 9 weeks and neither was dewormed. I took Puddles immediately to the vet once I picked him up and it was found that he was innudated with hook worms. He had very little energy and a little appetite. You should really bring her to the vet, it could be some type of worms that have her feeling lythargic and lazy. I really recommend that if she hasn't been dewormed yet.