Head and hands and on a fighting day fight.
She's creative and hits shots to places on the court where the ball is a rare visitor, she's pretty fast, she can hit, on a good day, really impressive winners on both sides, she's got a good serve, the serve and her playing style are unusual which takes some getting use to. Add to that, she can beat top 5 players if she can get them into a rally - they run out of ideas before she does. If she can delay them long enough the effort of playing her (particularly if the match develops into long rallies) and the necessary mind game tends to produce mental fatigue in the player on the other side of the net (look at her second set comebacks and third set follow throughs in her major wins)
Put her up against a power player playing fast and error free in ball machine mode and she just won't have time to entrap them in her game. Put her up against one who is making a few errors, playing a bit slower than Lindsay was today, still has "wild thing" or "manic depressive" lurking inside them and who is tempted or forced to take her on in a series of rallies and Patty can win.