Now that Manohar is visualizing this process in detail, he feels a bit concerned about Merrin's chances. You're supposed to construct a spell and hang it, on a magical scaffold that you build, over a spellsilver-inked diagram in your spellbook, and the first stages of this process usually involve an older apprentice constructing the scaffold and spell, and leaving it there while a flock of students wave their hand over that spell and try to feel it and try to manipulate it. That Merrin can't do that, doesn't quite rule out her having her own magic that can pass through her antimagic barrier, but it does sound like the standard teaching method wouldn't work.
Manohar's best idea: Somebody shows Merrin an illusion overlay of what's going on while an otherwise not-too-experienced wizard slowly constructs their scaffold and spell for Detect Magic, the first cantrip apprentices usually learn for obvious reasons, while also telling her the math used for inferring the non-visible parts and describing the observer's guesses about what's currently happening to those. Then, Merrin can be given a spellbook page for that, and... try to do the same thing even if she can't sense anybody else's magic? Even an apprentice running Detect Magic would be able to notice if Merrin succeeded in a preliminary way at moving any magic outside of herself in a way that stuck onto where the potential scaffold should be above the spellbook.
But Manohar really has no idea how you'd start on doing that, if you didn't know what magic felt like, and had no way of feeling that sensation for the first time.