There is a difference between borrowing something from you and claiming a relationship with you that you haven't consented to. If, let's say, a coworker buys the same top as you, that'd be inoffensive imitation; but if she repeatedly reproduced your choices, mannerisms, style, and monitored your every move, that'd constitute a completely different scenario.
Envy is not only wanting something another person possesses; sometimes, it also involves some form of resentment toward the person who possesses it. That way, the object of desire becomes entangled with the person who has it. You are not really envious if you don't feel some degree of (repressed or not) aggressiveness toward the person you are envious of.
Hedy, in this case, is pictured as a 'single white woman', making it really easy for us to identify the archetypal figure of a woman who feels entitled to everyone's attention, struggles with boundaries, and has that sort of 'desperate' vibe to her. That instantly gives us the ick.
People who feel socially inadequate might think the only solution is to imitate someone adequate so perfectly that it finally makes them be that way. This happens everywhere, as there are more socially inadequate people out there than we'd like to admit.
From her perspective, anyone perceived as adequate or popular is an asset, and her answer. This kind of identification can theoretically help you develop a stronger self; to some degree, we all do it. We identify with role models, influencers, and all sorts of people, and they mold our behaviors. But sometimes those role models also create dependency, and our relationship to them becomes problematic, if not creepy.
The envious person might experience her similarity to her coworker as reassuring because, to her, it means she will obtain more social power, while the other person experiences the same behavior as invasive.
Perhaps this woman doesn't want to be similar to her coworker, and she just wants a relationship with her. That's what makes her socially inadequate in the end, because she clearly doesn't know how to build a friendship; apparently, all she knows is forcing herself into conversations or imitating someone until it creeps them out.
I know being on the receiving end of this type of conduct can be really disturbing, but I always found peace in the fact that precisely what makes those people creepy cannot be erased; they can never imitate you perfectly because they are inadequate in essence, and they've earned that you don't want a relationship with them.
So if you leave them be and don't get too stressed out about someone copying your identity, life will put people in their places, and likely everything will go back to normal. Trust me, I had a classmate in high school who copied everything I did, and literally was intervened with by teachers about it.
Human groups put everyone in their place, and in the best-case scenario, it helps people understand how to integrate more positively!