Rhaelys might not have the name of her house, but that doesn't make her any less of a Targaryen. She is as much Targaryen as Aegon is, Mushroom writes, which is perhaps what drew him to her in the first place. Targaryen blood calls to Targaryen blood: if that blood is not poisoned with Hightower lies.

(If we share the same blood, and your blood is my blood, how much of our blood is poison?)

Rhaelys Velaryon came of age in 123 AC, as that was the year that she turned three and ten years old. Her first flowering came not much later. The daughter of Rhaenyra Targayren, her coming of age marked the beginning of her true tenure as the heir's heir. Rhaenyra raised Rhaelys to rule after her.

By wish of the princess, a betrothal was made for to prince Aemond Targaryen, her young uncle. Rhaelys was not unhappy with her betrothal, but a small part of her had wished that she could remain unmarried for the rest of her life.

She would become Queen, and following her her brother Jacaerys would rule, together with Alicent Hightower's daughter Helaena. It would give everyone what they wanted. Alicent's blood would sit the throne, and the rightful heir would keep her right.