it's a standard provision as it reflects the limits of the Internal Revenue Code, section 422(d)
422(d) $100,000 per year limitation (1) In general To the extent that the aggregate fair market value of stock with respect to which incentive stock options (determined without regard to this subsection) are exercisable for the 1st time by any individual during any calendar year (under all plans of the individual’s employer corporation and its parent and subsidiary corporations) exceeds $100,000, such options shall be treated as options which are not incentive stock options.
(2) Ordering rule Paragraph (1) shall be applied by taking options into account in the order in which they were granted.
(3) Determination of fair market value For purposes of paragraph (1), the fair market value of any stock shall be determined as of the time the option with respect to such stock is granted.
But she only exercised 17,506 options, it possible she only exercised the options vesting in 2013 and some of the options vesting in 2014, which might all be under the 100,000 per year limit.
It's possible these are ISOs, but I didn't see anything definitive in the proxy either way