Do any airlines publish their policy on CRM / Do Not Pair?
I worked in the industry for 16 years with multiple airlines.

In two of these we had 'do not pair'. Most airlines use computer systems to do their crew planning. In the systems I have used, you can enter against each crew member, others they should not fly with.

The decision as to the use of this laid with Fleet management or Cabin Crew management and was only used in extremist.

In both airlines however, this was not a documented procedure.
Hope this helps.