Just so you know, women/females can be very uncomfortable being in places where they are alone like parking garages, elevators. parking lots, any place where they can suddenly be alone where they may be approached by someone. Waiting for a woman to be alone to speak to her can send her a concerning signal. Keep in mind most predators prefer to single out and get their targets alone. Any woman that has experienced something negative where she was singled out when she was alone will NEVER forget how that felt. (Something I have experience myself a few times actually when I was younger tbh).

While you have explained that you tend to be shy and feel uncomfortable due to believing you are not very good looking etc., you probably unknowingly find it a bit easier to approach others alone and quietly. You don't mean any harm, however, it's important to understand that predators tend to single people out and may even not approach a person in front of or around others but instead try to be around their target when their target is alone.

In all honesty, this has nothing to do with your looks either, yet, you decided to sit and think about what you FEEL keeps you from being accepted. Truth is, there have been plenty of people that were admired and appreciated that did not possess all of what is deemed to be "good looking". What comes to mind for me is Jimmy Darante, Danny Devito, the characters in The Big Bang Theory, Andy Rooney, and countless others that became character actors that people grew to enjoy in different stories and movies that had something endearing about them even though they were not the guy with all the looks. Instead, what people focus more on is how another person leaves them "feeling". That is what you are focusing on now that the HR talked to you, "how that makes you feel".

There is NO crime in seeing another person you find attractive that you would like to know better, or even date. It's more about how you behave that can make that other person feel uncomfortable and often it's when they notice you looking at them and only saying something when you see them alone too. It's also how that person may have experienced something in their own history that frightened them too where someone singled them out in some way leaving them "feeling" very frightened and vulnerable.

You are only in your mid twenties and just learning your way around the social work environement. My guess is this female coworker is around the same age and trying to figure out her own way of learning about the work environment for herself too. This means she needs to learn how to feel safe in a parking garage, in an elevator, and around other coworkers where she can gradually learn to feel more comfortable too. Most likely, her focus is not on finding some guy to date, but instead to learn how to feel safe just going to work and learning what that's all about.