AITA for hooking up with my best friend's little sister when we were locked in a bank vault together?

I'm a firefighter by trade—though my side hustle is being a phoenix. As you can imagine, not every woman is on board with hooking up with a shapeshifter. Luckily, I have my brothers and my best friend for company. Unfortunately, the aforementioned best friend has tasked me with keeping an eye on his little sister Misty, the girl who used to have a childhood crush on me. A lot has changed since then. Now, Misty is a bank teller with a sassy mouth and curves that don't quit.

I could have kept my hands to myself, but then a bank hold-up goes wrong, and Misty and I end up locked in the vault together. Alone. For hours. I mean, I'm a phoenix. I can't ignore heat...especially the smoldering looks Misty throws me. So, one thing leads to another, and let's just say, the situation between Misty and me goes up in flames...in the best kind of way.

But now her brother has questions and I've got to figure out how much to tell him. AITA for wanting to risk our friendship because I can't stop thinking about his little sister, and I don't want to keep Misty and me a secret any longer?

Readers love Ashlyn Chase's paranormal romance:

"This story has it all, laughter, tears, magic, and sizzling heat."—Night Owl Reviews, 5 Stars, Top Pick!

"Snarky dialogue and sizzling heat."—Booklist