Here's what's going on. Her IG account may, in fact have been hacked. This happens. She's obviously afraid and angry. She is the kind of person who thinks she can solve all of her own problems, and found the licenses section of the app, which included something with a nonsensical name (libcurl) and a domain "haxx.se". Despite having known that haxx.se is for libcurl basically forever, I occasionally see it and associate it with gray or black hat stuff before I remember. So it's not at all surprising that a non-initiate saw this and thought it might have something to do with her IG account being hacked.
Daniel says his reply to her original email was "clear and rational". It should have been "understanding, compassionate, and patient". This is someone who is seriously freaked out, because her livelihood is at risk, and based on the fact that she went digging through the app, she is probably having what a shrink would call a "crisis of control". So here's what the author should have done:
1 ) Patiently explain what libcurl does (it let's programs request web pages, just like a browser). Explain that he's the author, but he's given it away for free. The license is in the app because he took pains to ensure that nobody can package it up with some slick marketing and sell what he's giving away free.
2 ) Acknowledge that haxx.se sounds kind of shady. Explain why he chose the domain. Self deprecating humor would be great here. Explain that despite this, all kinds of apps use libcurl for perfectly benevolent purposes.
3 ) Explain that he has nothing to do with instagram (commenters have suggested the car parts analogy, which seems like a good plan).
4 ) Finally, and most importantly, link her to their hacked accounts page! They have people paid to deal with this stuff, who are much, much better at dealing with panicking laypeople.
There is a lot of "reason good, feelings bad!" stuff in the tech community these days. It makes people see us as a bunch of borderline autistic[1], self centered, stuck up, evil nerds. Many of us, myself included, were terrible with social interactions and dealing with our feelings at some point in our lives, so the finer points of human interaction and emotional thinking left a bad taste in our mouths. But we've all grown up. We aren't social rejects and evil nerds anymore. We have lives, careers, friends, and family. We need to let go of the stuff we suffered in our youth, forgive those "stupid popular kids", and learn how to be nice.
[1] In the sense of the popular conception of borderline autism, not the clinical condition, which generally doesn't make you a jerk.