This topic is inspired by a discussion on BoardGameGeek, but I figure there's more chance of an official clarification here. (I'm pretty sure the old FFG site had a means to ask questions of an FFG representative, but there doesn't seem to be one available now.)
We know that there are cases in which a hunter resupplies without actually drawing any cards. If a hunter resupplies in Castle Dracula, no cards are drawn, and a character might resupply in a small city but decline to draw an event card (for fear of it helping Dracula). It is rarer, but a hunter might even choose to draw no cards at all in a large city or the Hospital of St. Joseph and St. Mary (perhaps wanting to avoid disturbing the distribution of cards in the Item deck).
However, my question: In those instances when Mina Harker resupplies without drawing any cards as per the normal resupply rules, may she use her special ability to draw an Event or Item card?
It might be argued that the use of the word "extra" in the description of her ability indicates that she cannot use her special ability unless she actually draws a card while resupplying. However, it can also be argued that the strict definition of "extra" does not indicate that the card drawn using Mina's ability be in addition to a non-zero number of card draws.
The FAQ does not cover this case, as the only FAQ question relating to Mina's ability examines only the case of drawing an Event card in a small city. (Strictly, English grammar tells us that a sentence containing an "if" clause says nothing at all about the case when the "if" clause it not met. This is why we hear the construct "if and only if" so often in the field of logic.)