Firstly wait for the morning and take it in to a panel shop to have a look before you make any decisions. Depending on how hard she hit you it might have actually damaged more than you think. My wife had a guy bump her and the bumper 'popped back out' so it didn't look bad at all. However the crash bar/stiffener, clips etc. were damaged and even after repair, the PDC sensors had to be changed.
If it is just spraying the bumper cover, then its not going to be much of a comment and can just be explained away as exactly what it is - a minor parking lot incident.
You could also do it privately but it might be obvious that the bumper has been resprayed and I'm wary of buying cars in plan with obvious paintwork that don't have comments... (my thinking being that I would rather see a 10K comment or even scratches/damage than a car that has no comments but obviously has had paint)
Privately, I remember paying 2500 to respray my Subaru bumper a few years back (metallic). I have a small trolley mark on the back of my M5 and I'm not committed enough to fixing it beyond some touch up paint since only I know its even there. Unless it really bothers you and you can't polish it out, I'd leave it.
I'll leave one more angle to this since you are mentioning values (and might be thinking of selling): If you are trading in the car, just see what value they give you as-is. My mate had this dilemma recently and the trade value as-is vs. a repaired car, relative to the added cost on your insurance for claiming (which is a long term consequence you will bear on everything you insure in future) was not worth fixing it for a relatively small difference in trade value.
