It's done all the time, but...
Your example is so short that I'd go with "her," because in that context it doesn't look like a deliberate shift...but. no, it isn't jarring as it stands.
But, sure, moving into second-person is often used for somewhat longer passages; especially popular in noir detective novels, where it often functions as kind of a faux first-person for passages within a first-person narrative: "You figure you'll always be able to handle the last ounce in that bottle, but in the morning you wake up on the floor, and..." (etc.).
Second person is tricky. It can be used for, as you call it, 'universal truths,' but it is a little bit weasely and overconfiding--the narrator isn't really owning the statement, but is rather trying to make it something we already agree on. It isn't an omniscient statement of truth (as opposed to what is said so explicitly in the opening line of "Pride and Prejudice"), but it also isn't the narrator saying, look, here's what I believe.
The fact that the narrator resorts to "you" and doesn't own the statement can be very distancing--used to good effect in "Bright Lights, Big City," where the continuous use of second person in what should be a first-person narrative gives a chilly, alienated, inauthentic effect. (Too much of one, some foks think--some admirers of the orginal story found it insupportable at novel length.)
The confiding, we-both-agree tone of second person is a little like having someone throw their arm over your shoulder while talking to you. It's okay if you're good friends, but it can be really annoying when you hardly know them and they start using that arm to steer you somewhere (like to a more expensive end of the used-car lot).