This wouldn't be the first time Melissa has hidden behind a mask. Remember when she dressed up at the Queen of Hearts?
We know a couple things about Melissa's involvement in this whole mess. One, we know she's really, really tangled up in it. Two, we know she's probably not telling us everything she knows. Seems pretty shady to us.
If Melissa accidentally killed Bethany Young, and if Bethany Young is somehow linked to Charles, there might be a reason that she'd want to be in contact with Charles. This would explain why Red Coat and "A" have joined forces. That is, if "A" is actually Charles.
Why She's Not Red Coat:
Melissa has allegedly been in London for quite some time, and we have to say, it seems legit.
You know, seeing as Melissa killed Bethany Young, wouldn't she be against Charles? Wouldn't she be trying to take him down?
On that same note, at the bottom of everything, Melissa is trying to protect Spencer. At least, that's what she says. If she's telling the truth, the last thing she would do is link up with "A."