Am I too skinny for a BBL at 5'1 and 123lbs? (Photos)

Thanks for your question. Based on your photos you don't appear to have enough fat available for a dramatic result form a Brazilian butt lift procedure. You can definitely improve your overall shape with liposuctiuon and fat transfer to the buttocks although you will not achieve the looks you're showing on your wish pics. You definitely have to choose your surgeon correctly and make sure that he/she has the training and experience to meet your goals with absolute safety.  Best is a Board Certified Plastic Surgeon with specialized expertise in this procedure.

Hello, thank you for the question and great photos.. after analysing your case.. I can say you're a good candidate for a BBL, this would give you great results and improve the look of your butt. Your wish pics are a little bit unrealistic, but trust me, a good doctor would give you a great result and get the best of you!

l recommend you to make an appointment with a board certified plastic surgeon to talk about your goals and anything you need to know.
Best of lucks and stay safe these days :)
Dr. Luis Mejia.

Thanks for the question. 
In this regard, I recommend you waist and back Liposculpture, getting better curves especially in the waist, improving your body contour.
Finally, I suggested take the fat we get and transfer to the buttocks and hips, to mold them and get better volume, contour and butt projection, is that we know as "Brazilian Butt Lift" (BBL).Kind regards