Again, a likely part of what went on here was that she got into a pattern of being anxious that she wouldn’t be able to fall back to sleep which became self-fulfilling. Her being able to sleep on the mat in your room, the knowledge that that is there and will work if she needs it, may have been all that it takes that when she wakes up (and she does … we all do … it is normal sleep cycles; we just don’t remember it) she is no longer nervous about it and can go right back down.
While not necessarily wrong, I don’t think anyone should take this sort of advice to heart. Because if you do, you will become absolutely neurotic and crippled when it comes to making any decisions about your child. “Is this the little choice that will land her in the therapist’s chair? What about this one?”
Do what feels right to you and right to your child and right for your family, and don’t spend time worrying about some hypothetical therapist chair far in the future. You can’t control that. For every kid who goes to therapy because their mom told them “Hey, I’m so proud you slept through the night!” there’s a kid who goes to therapy because their parents never said they were proud of them. Or whatever. Seriously, this will make you crazy. Just don’t even.
We still a cartoon on our wall from when our 27 year old was a baby:
Two Mom’s holding their toddlers. One saying to the other “I’ve stopped trying to give him a perfect childhood and now am just trying to limit what he says about me on the couch.”
Me personally, I’d be trying to draw a very clear distinction between the parts of the situation over which she does have some control, and the parts over which she doesn’t. She does have control over, for example, whether she wakes up the rest of the household - and I think you’re dead right to highlight that. But she has no control over whether she’s asleep or not, and making her feel like she does will only add to her stress. I’d be making it very clear that I understand she doesn’t have any control over that element, but that the two of you together can find ways for her to control how she deals with it.