Hi Leminni,
It sounds like you're struggling with how to be a good friend to them, while also maintain your own mental health. From what you've said, I think you've been doing a good job so far, so thank you. I certainly don't think you're heartless, and posting here looking for ways to help is evidence of that!
It also sounds like you're dealing with compassion fatigue/burnout. It's a very real and is not uncommon.
Looking after yourself should be your number one priority.. I struggled a lot with this a couple of years ago. A saying really helped me, as it had begun to impact every aspect of my life: "Don't set yourself on fire to keep others warm."
Listening to them is a very special gift that you give. Often, just talking to someone, without feeling like I need to fix anything, can take me from being in a really bad head space to being in a level head space.
I know it can be frustrating sometimes, especially when it seems like they aren't listening to things you think might help them, but in the moment, it can feel like nothing will help.
Are you familiar with this proverb? You can lead a horse to water but you can't make him drink.
Ultimately, your friends will need to do the work, you can only try your best to show them the way.
Instead of telling them to back off, I think it's very reasonable to ask for some space. You have said they are online friends, could you choose to be less available? Set your status to invisible or offline for a while. If they do ask to talk, let them know you care, but tell them that you can't right now, but in an hour you can (for example). The goal is just to create a bit of breathing room for yourself.
I hope this helps.
Isaac
