Conservative lawyer Jenna Ellis has agreed to cooperate with prosecutors in the Arizona “fake electors” case involving 11 allies of Donald Trump, and a legal expert said her testimony could put new pressure on Rudy Giuliani to flip against his former boss. The former Trump campaign lawyer signed a cooperation agreement Monday after prosecutors agreed to dismiss four pending felony charges against her. MSNBC legal analyst Lisa Rubin told “Morning Joe” that the favorable terms offered by state attorney general Kris Mayes could be an ominous development for Giuliani. “I think the plea deal was ex…