Wow, that was a lot more replies than I was expecting.  Thanks everyone for your feedback.  There are a lot of suggestions here that could work.  I'll be running a decent bit of these by her to see which one sticks the most. 

I'm definitely glad I posted as I probably would have let her get away with being too powerful based on the math I was using.

I also learned a few things about the rules, so thanks everyone.

I'm a brand new GM to any type of table top game.  I picked this up because my wife said she would play it because she's a huge Dresden fan.  I got a couple of other people involved and we just did our initial city/character creation.

During character creation my wife said that she wanted to throw lightning around.  I explained that she could use the focused practitioner, but she couldn't take refinements to be better at lightning.  So she would probably want to take evocation so she can refine it.  She asked why she couldn't refine just her lightning/air powers and why she had to take evocation and the extra elements.  She wants to roleplay someone who is just REALLY good at one element.

So, I wanted to ask you more experienced GMs if making a custom power or bending the rules on this kind of thing causes serious issues.  If my math is correct then about the highest obtainable point for a single element of focus is about 9. 5 from convocation being rank 5, and 4 from double refinements with 4 lore.  (Of course focus items could push that higher, but those are both obtainable for each).

So I thought of giving her a 1 refresh power she can take that gives 2 shifts on lightning spells.  With a cap of twice.  And a matching power that gives her 2 shifts on discipline rolls.  So she'll have to spend 4 refresh to hit 8 conviction/discipline on lightning rolls.  Which is about what the evocation would cost (3 refinements +1 for evocation).

Does that sound reasonable?  Or am I opening up a can of worms?  Is there a better way to handle this focused practitioner cap?