you (female)
妳 is a rare kanji that specifically means 'you' when addressing a female. Its meaning is narrow and personal, used as a feminine second-person pronoun.
妳 combines 女 (woman) with 尔, which likely contributes a phonetic element. The character was created to specify a female 'you', parallel to 你 for a general or male 'you'.
The left side is 女 (woman), and the right side 尔 resembles a person. Think of pointing directly at a woman and saying 'you' — that's 妳.
For ダイ, imagine a woman named Diane being addressed directly: 'You, Diane!' — Diane -> ダイ, and the woman radical 女 reinforces the female 'you'.