Hi Amy,
you are correct in your assumption that the users should go to the mnetwork_users table with the corresponding blog id as network id.

Though this approach works, I would have done it using WP_User_Quey or get_users to make sure that we are fetching the users for the specific blog id.

I do not consider xprofile data field to be a reliable source for users on the subsite(unless they have added some data).

Marking it as resolved now.

Thank you
Brajesh