**Core Concept**
The clinical presentation of primary amenorrhea, advanced breast development (thelarche), and underdeveloped pubic and axillary hair suggests a disorder of sex development, specifically a condition characterized by an imbalance of sex hormones.

**Why the Correct Answer is Right**
The girl's symptoms are consistent with **Androgen Insensitivity Syndrome (AIS)**, a genetic condition where individuals have a 46,XY karyotype but are resistant to androgens. This results in a failure to develop male secondary sexual characteristics, despite the presence of testes. The testes produce androgens, which are converted to estrogens in peripheral tissues, leading to breast development and growth of the uterus, but not the development of pubic or axillary hair.

**Why Each Wrong Option is Incorrect**
**Option A:** **Congenital Adrenal Hyperplasia (CAH)** typically presents with an excess of androgens, leading to virilization of external genitalia and early onset of puberty, which is not consistent with the girl's presentation.

**Option B:** **Turner Syndrome** is characterized by a 45,X karyotype and typically presents with short stature, ovarian dysgenesis, and lack of breast development, which does not match the girl's symptoms.

**Option C:** **Premature Ovarian Failure** would result in estrogen deficiency, leading to delayed puberty and lack of breast development, which is not consistent with the girl's presentation.

**Option D:** **Kallmann Syndrome** is a condition characterized by delayed puberty and anosmia, but it does not typically present with advanced breast development.

**Clinical Pearl / High-Yield Fact**
In patients with primary amenorrhea and advanced breast development, it is essential to investigate for disorders of sex development, such as Androgen Insensitivity Syndrome, as these conditions require specific management and counseling.

**Correct Answer:** C. Premature Ovarian Failure