I'm 5'2" tall and currently I weigh 100 pounds but I would like to get BBL with fat transfer?

This is hard to judge without photos. I had three patients in the last two weeks who were about 115 and got at least 700 cc per buttock in each one. I perform about 500 Brazilian buttlifts each year, and this
procedure is the most surgeon dependent plastic surgery procedure. Find
a plastic surgeon with ELITE credentials who performs hundreds of
Brazilian buttlifts each year. Then look at the plastic surgeon's
website before and after photo galleries to get a sense of who can
deliver the results. Kenneth Hughes, MDLos Angeles, CA

Hello dear!!
Thanks for the question and provided information as well. 
Unfortunately, without pictures, it is very difficult to give you a proper answer. 
In general, you need to be physically healthy and at a stable weight, have realistic expectations, be a non-smoker and your BMI needs to be 30 or less. l recommend you to make an appointment with a board certified plastic surgeon to talk about your goals and anything you need to know.
Good luck :)

In order to determine if you are a good candidate and have enough fat reserves, you would have to be seen in person. Good luck.