As busty as she looks, I don't think she has a back problem.
1. Whether she has F cups or G cups, every pair has different texture (denser or not), and among playboy models she definitely stands out, but she is just "average" among owners of huge tits. Many owners of even bigger tits are still intact.
2. I cannot say Ukrainian models all keep their tits, but women from her country are not known for getting BR (if at all). She obviously enjoys her work, so if you would talk to her one day and bring up BR, most likely she would be confused "why even?" Here you go.