I think Part was about 29 or 30 when she was promoted. She was never out for a long period of time due to a substantial injury during her soloist years at ABT, to my recollection. Steady wins the race, as they say.
This is either outdated paternalism on the part of ABT ("it's for her own good") or else they're afraid their workers compensation bill will go up. Many ABT dancers have been injured, some short-term but multiple (Cornejo), some longer-term (Seo, Hallberg), and same at NYCB (Jenny Somogyi comes immediately to mind.) After dancing 10 Auroras in 30 days in Royal Ballet of New Zealand's Sleeping Beauty, it is apparent that Abrera has the ability to sustain herself in full-length ballets.
(On a completely different topic, I'll be out of town just long enough to miss ALL the performances of the new Ratmansky ballet(s), so I'm looking to my fellow Alerters to keep me informed. Thanks in advance, everyone.)