Is this achievable with a BBL? I’m a pretty thin girl. I weight 115-125 and I’m 5’7. (Photos)

You can get a modest increase in buttock size and shape with liposuction of the abdomen, sides, back, and legs and transfer of that fat to the buttocks.  This procedure is highly surgeon and technique dependent. The thinner patient requires an expert at liposuction to remove as much fat as possible while leaving the skin smooth. 
Find a plastic surgeon with ELITE (education, experience, training, certification by the American Board of Plastic Surgery) credentials who performs hundreds of BBLs each year.  Then look at the plastic surgeon's website before and after photo galleries and read patient reviews.
Kenneth Hughes, MD, Board Certified Plastic Surgeon
Los Angeles, CA

Hello karleesteel,
Thanks for your photos and questions! I would suggest you consult with a board-certified plastic surgeon about your specific needs and aesthetic goals. In a first consultation, your surgeon will evaluate you as a candidate for buttock augmentation with fat grafting (BBL) and clarify what fat grafting can achieve for you. BBL uses fat transfer to provide a more curvaceous buttock without the use of an implant. An assessment from an experienced plastic surgeon in both, BBL and Vaser lipo procedures, is highly encouraged since VASER liposuction is commonly used to sculpt the surrounding area and collect the autologous fat (from your own body) to be injected. I do recommend gaining some weight if you desire to have a larger buttock since the amount of fat to be transferred will be dependent on how much your surgeon can harvest.  In my experience, one is able to harvest more fat using the VASER liposuction system (at 50% amplitude using the Vaser Mode).  Hope this is helpful! Dr. De La Cruz.