Is this only the top of her foot?
Or the bottom of the foot?
Which side of the foot (big toe or little toe) seems to be worse?
Well, certainly the neurologist is a specialist in this area, so you should get a better idea here.
When numbness is a symptoms, it usually is either 1) poor circulation to that area, or 2) nerve entraptment/inflammation.
Given that this is the top and bottom of her foot -- it would mean two separate nerves would be affected, and it isn't clear how these nerves would get affected from the surgery you mention (since the nerves would have to be compressed at the ankle level or above, like in the lower back.
And certainly -- a check of the circulation can be done in the doctor's office.
And further testing, such as a EMG test can help to see if there are nerves that are not functioning correctly.
But regardless -- the exam by the neurologist should give you a better clue as to what is going on here. It seems very unusual for this symptom to be related to a toe surgery.
Well, to get numbness in both the top and bottom of the foot -- two separate nerves would have to be involved. While possible, it seems to be a strange coincidence that this would happen at the same time (one is on the top of the foot, the other goes near the inside, under the ankle).
So, if circulation is ruled out, then nerve entraptment or inflammation is likely. But the question is where? After the detailed neurologic exam, the neurologist should be able to figure out a likely place, and do further testing to see if this is something which can be treated.
Well, an incision in the inside part of the ankle, could affect a nerve in this area, the tibial nerve.
But this seems unlikely, since injury could also cause weakness in movement of the toes.
But of course, an exam is best here since over the Internet, I am simply making an educated guess.