I think every office has a Gina.
Interestingly, most offices have a you too — the person who gets hijacked by Gina and feels rude setting boundaries. Often, it’s for exactly the reason you cite: You happily chat with others, so it feels wrong to set boundaries with Gina that you’re not setting with other people.
But you can and you should, and it’s not unfair or unkind to do it. Gina is using your time in a way that your other colleagues aren’t. She is routinely negative and critical, becomes even more negative when you disagree, and has ignored all your cues that you’d like to get back to work — three things that probably aren’t the case with the co-workers you’re happier to chat with. You’re justified in putting limits on conversations and people that sap your energy and affect your quality of life.
It’s worth noting that for all the time you’ve invested in listening to Gina, she doesn’t seem to have invested much in listening to you. Gina is treating you like a vessel she can vent into — but where’s her interest in your life, your experiences, your feelings? The relationship sounds awfully one-sided. She gets to feel better by venting to you, even though it makes you feel worse, and she never does anything to replenish the good will she’s using up. It’s reasonable for you to decide you’ve had enough.
As for the mechanics of how to begin setting boundaries when you haven’t previously — you’re at work, and work gives you an easy excuse. That can sound like one of the following:
“Sorry, I’m swamped today and really can’t talk.”
“I’m on deadline, and I’ve got to get back to it.”
“I’m right in the middle of something and don’t want to break my concentration. Can you email me instead?”
“I’d better get back to this. I’ll see you later.”
I suspect you haven’t been saying things like this, because, in theory, you could make time to talk to Gina — like you do with other colleagues. But these types of statements are perfectly acceptable at work — even when they’re not 100 percent true. You probably do have work-related things you could be spending your time on rather than listening to Gina’s complaints, and you’re not wrong to tell her that you need to use your work time to actually work.
If you’re worried that it will feel strange if you go from giving her free conversational rein to erecting firm boundaries, you might have an easier time if you first set the stage by saying something like “I’m heading into a busy period and am not going to be able to chat as much as I used to.” Or “I’m trying to be more disciplined about not chatting so much at work.” That way, you’re letting her know what to expect, so your future demurrals will be in context, and, maybe more importantly, you’re giving yourself a framework to feel more comfortable asserting control over your time.
Keep in mind that with chat messages or requests to video call, you have the option to ignore the requests. It doesn’t sound like Gina is messaging you with lots of urgent work items, so you don’t need to instantly respond to everything. If you reply at all, let it sit for a few hours or even until the end of the day, then respond with “Just saw this, was tied up with work.” It’s the workday, so you are tied up with work — even if you aren’t breathlessly racing to meet a deadline. You get to decide how you’ll allocate your time at work. Not Gina. In fact, it might help to look at that as part of your job — since it is!
If you try these methods for a while and Gina runs roughshod over all your boundary-setting — which isn’t the most likely scenario but is possible — at that point, you’d need to get more direct. There’s no reason you can’t just lay it out for her: “I’ve got to be straight with you. I’m really drained by this much complaining. For the sake of my mental health, I can’t be the person you vent to anymore.” If she’s affronted by that, that’s okay. It’s a reasonable thing for you to say, and you don’t need to manage her feelings about it.