Awkward yes and especially awkward if she was arguing with HF and speaking loudly - 15 calls to his phone and then dead silence. Awkward yes indeed.
I accept that this characterization of CM's behavior on the walk ("she was talking on the phone loudly and sounded upset") is perhaps true. But unless it's corroborated by whoever she was talking with, I wouldn't use it to rule out other possibilities, since our knowledge comes from EA's story (who has been found to be, and admitted to being, untruthful repeatedly in what he has told). EA clearly has an agenda in fuzzying up the facts, to make it hard to perceive what really happened, and this may or may not be a less-than-truthful claim as well.