Tell her to shut her pie hole, or you'll do it for here and if she says anything about this in public, you'll remove her valve stems via a switch blade!
Or if you actually feel the need to justify the price increase, you could tell her that you didn't realize that the time if would take you in your photography work and the price of equipment would have you working for minimum wage.
This is a guesstimate, but let's look at this.
$125 for a photo session.
Session booking - .25 hours Face it, 15 mintues to convince a client to work with you is cake sometimes
Session - 2 hours Setup, tear down, shooting, dealing with clients
Editing - 1 hour This would be very simple editing for say 20 images. This doesn't include a lot of touch up.
If you look at a very simple estimate like that, you're looking at 3.25 hours and that's not including post processing, deliver, and depending on where you shot, gas expenses. $125/3.25 is $38.46. I don't know about you, but that's not much more than I make at my day job and at that rate, to pay for even $5,000 in gear, you'd be looking at $130 to break even with basic photography gear. At that point, it's not worth your talent and hard work put yourself in a position to work your ass off for nothing. I know people who have paid over $5,000 for a single wedding photographer. It's because they recognize the value in their work. You'll always have some potential clients that don't and that's why they'll always be potential clients and not actual clients.