As Shiho Miyano she wouldn't be able to be friends with the Detective Boys, and she very obviously cares for them. Examples needed? Every time she's with them, she tries to stay away when she senses danger because she doesn't want them getting hurt. And Ai is more like a child inside; she gets scared easily, she's dependent, and she hasn't experienced many things that normal people have. Not interested in kid things? Maybe she is an adult, but she is friends with the DB and nobody can deny that. She has fun with them, and it proves that she's a kid at heart. She's enjoying life RIGHT NOW. If the BO disappeared, she'd be perfectly happy. As I said before Shiho Miyano died. She's not coming back. Ever. Ai already let go of her.
And why don't we add Heiji to the 'Who's better off with Shinichi?' list? I really wanna! (I'm in a huge HeiShin mood right now after seeing this drawing.)