User blog comment:JmLyan/Fortuna, the Lady of Luck/@comment-10768370-20150612070256/@comment-7481207-20150612102555

As specified in the ability details, the E blinks 2.5 seconds along the currently issued movement path. If that path takes less than 2.5 seconds to complete, the blink will stop at the end of the path. So you will only blink into a tower if you ordered Fortuna to walk into it before casting E.

All spells reflected by the ultimate will be able to hit Fortuna's enemies while ignoring her allies.

And as I mentioned to Gutsy below, the AP ratio is just an added bonus to allow her to get AP items that synergizes with her, like Void Staff, Lichbane and Luden's Echo. It is nonetheless higher now, as it was too weak before and its early game lower values punished her already weak early game further if she rushes one of those items (or a Morellonomicon for mana and CDR).