This sounds like premature adrenarche, however with a bone age that is advanced even if her age is not alarming for her physical findings I would consider a small workup. Firstly sometimes the bone age needs read by a pediatric radiologist, next see if the endo will see you, even if they see you themselves in 4 months instead of your pediatrician. Labs that might be helpful will workup for the important causes such as abnormal rise in adrenal hormones, the other concern we have is if these male hormones that are becoming active at a slightly sooner tempo will prime the brain to stimulate the female hormones and trigger true puberty (menses etc).
So labs that are helpful include a 17-OH progesterone, dheas, androstenedione, sometimes thyroid functions and sometimes testosterone (free and total) and at times I get insulin levels since sometimes insulin resistance is a trigger for turning on the steroid production a little early in the adrenal gland-usually seen in obese children, and sometimes premature infants later in childhood due to their adrenals being primed for stress per se!
Bone age should be repeated about every year, monitoring growth is key, if her growth velocity is increasing she may need further testing.
Follow up - our pediatrician called and said she'd like to just monitor this for now, and she will check her growth again in 4 months. Is this how you would proceed as well?