Do you actually use LinkedIn? You seem to be assigning a connection with some sort of profound meaning that it simply doesn't have. Indeed, if you follow LinkedIn's standard user flow, it will generate connection invites for anyone who you've ever corresponded with and saved as a contact on your email platform. If you get invites that you don't want to reciprocate, you ignore them.
And isn't it glorious irony that someone in the business of networking complains about someone trying to network?
Add that LinkedIn allows you to restrict who can even send you invites (which this woman didn't use), and who can see your connections (which is apparently the grave concern here).
Sorry, this woman was obviously having a very bad day, with a strange hint that they may feel threatened by youth, and decided to explode on a stranger -- in a very inappropriate and tacky way. There is nothing "right" about their action.