extract below... is she correct?
Reasons exist for such rude behaviour. Slate
attempted to explain the phenomenon, but if your gut instincts have told you some element of superiority is involved, your gut was right. Polite, secure people do not correct other people’s grammar. If they have the meaning of what one is saying in conversation, most listeners will overlook slight errors. Unfortunately, we don’t always talk with “most listeners.” Sometimes, in person, online, and against our better judgment, we talk with snooty, self-appointed, and insufferable grammar police.
What’s Really Happening
Behind all grammar corrections, back-handed compliments, and “it’s-only-a-joke” jibes
lies hidden anger. When a Grammar Bully corrects your grammar (especially strangers online), you can rest assured that you are not the cause of his anger. Your word usage was simply the trigger of that anger. The Grammar Bully is in need of companionship, so publicly correcting you sends the homing beacon out to other Grammar Bullies. Grammar Bully is ringing in the friends with whom he can bond over mutual hate of the their/they’re misstep.
When we are
angry or stressed, a bonding hormone called oxytocin is released, urging us to form social connections with other humans so as to better our chances for surviving the cause of the stress. A Grammar Bully is feeling insecure in some way, and the insecurity is driving her to gather up friends. Many observers may think the Grammar Bully is about belittling others, but really, the Grammar Bully is just looking to find other Grammar Bullies because she is feeling angry and/or stressed.
Anger can be subconscious and many times it is. We are discouraged from expressing anger when out and about in polite society, so we suppress it. Unfortunately, anger is one of those emotions that bubbles up to the surface. Grammar-correcting behaviour is one of suppressed anger’s outlets.
. I thought I had a lot of spare time on my hands. 
