Can I get a second round BBL just to fill hips?

Allow me to answer your question as best i can without any photos. However, please keep in mind that an in-person consultation with physical exam, or at least a virtual consultation, is first necessary before any legitimate evaluation or final surgical recommendations are made.

In general, cosmetic hip implants are the most reliable, predictable, and permanent option for filling in the hip dips and creating more of that feminine hourglass figure, whether slim or not. On the other hand, fat transfer to the hip area tends to survive quite poorly in most patients and thus produces only short term results (often less than 10-12 months). Injections/fillers such as Sculptra or hyaluronic acids are cost prohibitive (i.e. guaranteed to be the biggest waste of money of your entire lifetime), short lasting and possibly deadly with high volume injections. Others such as silicone/PMMA/hydrogels/etc are cheap but extremely dangerous and a personal commitment to a life of serious and sometimes deadly consequences. Typically hip implants are best custom designed and created for each individual patient’s anatomy. Because an extremely few number of board-certified plastic surgeons perform this procedure, make sure you seek consultation with a reputable and experienced cosmetic hip implant specialist. You may have to travel a long distance from home to find this particular surgeon. Glad to help.

Dear Januaala,
it is hard to tell for sure without an examination. generally speaking, it is possible to transfer fat only to hips. If you are considering surgery, I would suggest you consult a board-certified plastic surgeon. Only after a thorough examination, you will get more information and recommendations.
Daniel Barrett, MDCertified, American Board of Plastic SurgeryMember, American Society of Plastic SurgeryMember, American Society of Aesthetic Plastic Surgery

Of course it is feasible for you to have a second BBL procedure with fat transferred just to the depressed hip areas without involving the buttocks.