Should I buy a chihuahua puppy for my 12 year old daughter?

My daughter wants a chihuahua because the are loving companions to play and snuggle with. She understands all that is involved with caring for this breeder in great detail. She has researched heaps about the breed on the internet and has ordered heaps of books about dog care and training from the library.She is not involved in any school activities,does not go out with friends so she has heaps of free time to care for a dog she is willing to spend all her free time with it daily and let it sleep in her lap while she does homework. I know she will spend all her time with it and clean up its messes and has been reading a lot about training dogs.She also knows a lot of information on choosing from a good breeder and has drawn up a feeding and house-training schedule for one. We are able to afford a good chihuahua puppy with vet visits and care supplies. She has also drawn up things we need to do to puppy proof the house. She gets mostly B grades at school. Though I'm concerned about if it is appropriate to buy a dog for a child. We got her a cockateil last year and she still independently takes good care of that bird. Should I buy her a chihuahua? I know she is very committed in caring for one for the rest of its life and knows it can live up to 18 years.