LOL, this is the worst idea ever. I can see that backfiring awkwardly.
NGL it depends on the execution but you're not wrong either. Either way. Whatever this "friends" intentions are & however the people disagreeing with me feel, understand this. This situation is obviously putting a strain on OPs relationship & further complicating issues with their mental health. I'm failing to see how this friend is "supportive" in anyway when they're the cause of this thread being born to begin with whether they're aware of it or not.
We can all choose to hide our head in the sand, offer our
additional support until her relationship breaks down under the obvious strain of this situation until OP shows up back here in an even worse position than she is now. Or, she can be honest with her partner & this other person. They're causing problems. Whatever their intention is, doesn't matter. This thread wasn't made for no reason. My original advice stands regardless, as much as she may not like hearing it, as much as it may come off as offensive or derisive. She should save/cherish her relationship & mental health because we're not all so blessed. Drop the friend.