"We went over to my dad's hotel to show off the ring," Tyler, 28, tells PEOPLE of her engagement to guitarist Brian Harrah. "He grabbed Brian and hugged him, and was like, 'Good job, son.' My dad absolutely loves him."
Her dad, of course, is Aerosmith frontman Steven Tyler.
Describing how Harrah, 31, popped the question to her, Tyler says: "[We] were just laying in bed and he stood over me and said, 'I want to spend the rest of my life with you.'"
"He had it in the box and got down on one knee," says Tyler, who first announced her engagement on her MySpace page. "It was playful. He's by far the greatest guy I've ever been with."
Tyler, who split from her husband of nearly two years, Papa Roach drummer Dave Buckner, in 2005, and Harrah, who has also been married once before, are planning a wedding for next fall – with half-sister Liv Tyler and her 3-year-old son, Milo, in the wedding party. "I'm hoping Milo can do the ring-bearing," says Mia Tyler.
Although the model, who is currently writing a book about her life, is now checking out possible nuptial venues, she's much more focused on another wedding detail, confiding: "I want to blow all my money on the dress!"