This reading is a little messy. This reading for 愛 is an exception, 媛 uses the kun'yomi reading ひめ, and 県 uses the on'yomi reading けん. Here's a mnemonic to help you remember this reading for 愛:
If you ask anyone outside of Ehime Prefecture what they think of princesses they'll respond with, "Eh" (え). They don't really care either way. If someone from Ehime heard that they'd says, "EH? EH?! Princesses are the BEST!"
I am from Ehime Prefecture.