Think about it:
Layla's power is to "know stuff". Her power allows her to know how storylines were before being retconned, and contact with her awakens those retconned memories from heroes.
Thus, what happens when Layla meets Spidey?
Wouldn't she remind Spidey that he was married to Mary-Jane, that they had a daughter, that he unmasked himself and all that other stuff that Mephisto erased?
How come Quesada didn't realize this?
How come Mephisto didn't realize this?
All it takes is a single Layla guest appearance to have this entire storyline come crashing down.
In theory, you're completely right.
In actuality... why would the writers ever make Layla Miller meet Spidey, knowing what they do about her power? Especially considering how obscure of a character she is. If the people making these books don't want One More Day to be undone, then they wouldn't do something to sabotage that. And if they do want to reverse One More Day, now or at some point in the future, using a character who up until this point has had virtually no connection to Spidey seems like an incredibly random and anti-climactic way to bring an end to this storyline.