I'm late to this but late is better than never.
I don't ship Shiho / Haibara with Shinichi, Mitsuhicho or anyone at the moment. For one, she's a smart, cynical, introvert and practical young lady. She knows very well of Shinichi's intense feelings for Ran. Mitsuhicho is not on par with her. Her interest in others like Higo or Ichikawa Ebizo are just fan regard.
I'm fine if she doesn't find that someone. If she does, the author would have to introduce a person who can empathise with her and associate with her regularly in order to build up that relationship. It can't come out of the blue.
@Lambrusco, that is a good candidate. However, I don't see her willing to meet him since the last "encounter" on the train. She actively avoids meeting him in one of the later eps. There is no gaurantee he wouldn't scoop her up and put her under arrest with his other association.