The exercising of her options was not "because of taxes". That's backwards. It's the exercising of options that can be taxable.
In this case, these are ISOs (incentive stock options) so there is no tax due upon exercise. (Unless the exerciser falls to the AMT, or did not meet the minimum holding period.) Her potential tax liability is when she sells the shares. Which can be immediately or X years from now.
There's no confirmation that exercises are a good thing. Or a bad thing. What they are are simply exercises of options.
Option holders tend to exercise when they intend to sell. You don't generally want to see selling by management. However there are many reasons to sell, not all of which necessarily mean the person feels the share price is overvalued given the company's prospects. Folks will notice the market did not (immediately) give much importance to the filings.
Market Data 
Markets 
AI
