Can anyone here offer some "advance" advice?

I just changed violin teachers to a slightly more prestigious one. She's extremely anal about intonation. She's so incredibly anal about it that she decided to stick me on scales until I can play it perfectly. Almost every time she tells me the note is off, I'm about the width of an electron off the right place. Honestly, she has some seriously sharp ears.

Anyways, I practice using the Boss DB90 metronome, which can play pitches. How do I know when I'm exactly on it? I went through it with her and sometimes it'd sound like I'm right on i, the note sounds clear and unwavering against the electronic tone, but she'd tell me I'm off by another electron (haha). Also, can anyone give me advice on how to play each note consistently?