Does the chihuahua you're watching have a kennel? If the chihuahua you're watching isn't used to a "safe place" (or a "save point," as I like to call it as a gamer
) Then transition will be very stressful.
Don't you worry about the chihuahua not understanding the rules. They are very intelligent and usually differ to other dogs over us humans as a "testing point" to their behavior. If you have other dogs that know the rules the chihuahua will pick them up no problem.
Only issue is: Chihuahuas are small. They know they're small, and they know they need protection. If you're watching the chihuahua and he/she isn't kennel trained, I would suggest you make a "safe alcove" for her/him to retreat to where he/she can get thier bearings again. Chihuahuas are notoriously exuberant but need a place where they can "run and hide," or feel "safe" where they can observe the pack's behavior without the pressure of "messing up." (Chihuahua's are smart in that way and really want to please!)