pat doesn't hold grudges, per se - her short rages leave as quickly as they came. but if you've taken something of hers (or, say, shot her in the head), there is no length to which she will not go to find you and exact retribution. even running across the wasteland won't save you. her second motto might well be 'leave no business unfinished'.
she doesn't have an especially friendly disposition, but she can read things well, and always has a mostly-faux smile ready for the authorities (unless it's the legion, in which case she has her trusty pistol ready). she's usually quick to help outsiders if there's something in it for her, especially information, but less inclined to do things out of the goodness of her heart. nevertheless, if it's been a slow day, she might as well find some lost child's plaything to take her mind off the mojave heat.