In #619 Erin describes her problem as "It's like there are parts the Watch isn't reaching." I took that as meaning "the Watch is being blocked", not "my magic is being blocked".
My guess would be that it isn't going to be important either way, but you're right, she did say that. My suspicion is that Erin had to say something that would justify her jumping into Cherry's mind, and that was the particular formulation of words that happened to come out. But I suppose it could be significant if there are going to be people who can't be taken with the watch.
I find it simpler to take the Jakobite's statement in #628 that it is "a bit of my personality I implanted in her" at face value.
I'm sure we're supposed to accept what (Erin imagined) Jakob said. I'm only really clinging to my explanation because I find it way hotter. But actually I find it simpler to believe it too, in as much as it seems possible to me, whereas what (Erin imagined) Jakob said simply doesn't. Not that I'm demanding realism here, you understand. But everything's relative.
