No, she can't be trusted. It may be that there is a "pact" between the two women and not gaining another ally for the family. Each woman must be getting something out of the friendship.
The only thing is the press gushed about Fergie being invited to Sandringham for Christmas, they made a big deal out of it, when Fergie has done that for years. What really was a change was Fergie was with the family at the Queen's funeral and Commital Service..that could be because of Camilla.