Super Little? She does have 33 MPen from morello and sorc shoes. And I'm guessing that blasting wand was going to built into the Void Staff.
Hmm... Frost Fang (20AP), Morello (70AP), Blasting (40AP), Athene (30AP) and Dark Seal (10-40AP). So 170-200AP without runes with likely her Q+E maxed out. That should be 360 max dmg on E, 390 max dmg on Q and 550 max dmg on a skill lvl 2 R. That's max dmg values if her MPen completely negates your natural MR.
Level 17 Varus has 38 MR naturally, and she has 33 MPen. Ignoring runes that might boost MR or MPen.
Level 17 Varus should have 1800 health though. Max values on Lux damage without weaving some empowered Auto Attacks in her combo should top out at 1300. Her passive bonus damage on autos is 200 max dmg which doesn't include the actual auto damage. So theoretically she might be able to full rotation Varus with two auto attacks weaved into her combo. Possibly. I doubt I could do it but I have often missed skill shots on stationary targets.
I'm wondering how much AP she might have in her runes. I'm not sure how it will boost her initial 1300 up too much higher, but it might be enough to get it that she only needs one empowered Auto Attack instead of two.