Yes, it really is all about attitude and intent.
Not just about helping.
With too many mothers/MILs, the attitude and intent is to over-involve themselves... do it 'my way', because my way is the right way... Show superiority, make the DD/DIL to be less than adequate, etc...
There is a fine line there, and, unfortunately, many mothers/MILs know just how to play it.
Either way, it is the daughters house... PERIOD.
It is the daughters house.
If the OP has stepped in and done anything.... vacuuming, making coffee, cooking, interrupting, etc.... before making absolutely certain that her daughter was comfortable and that she had some kind of permission. (even if just clearly implied) That is, without a doubt 'overstepping'.
I can remember when, years ago, I and my husband kept my sister's young children for a few days, mostly in their home... So, nope, not just a visit... but, myself being left in total charge.... Nope, I didn't re-arrange her kitchen, change her coffee, re-fold her underwear... She made it clear that even though the house could def. have used a lot of attention at that time, that she really didn't me to be messing with anything. Yes, I did the basics, as I felt I needed too... Washed dishes, vacuumed... And, even then, because her personal feelings, I think it was hard for her not to feel that I had overstepped... With some people they are not as comfortable, and it is easily to feel their space is kind of violated.
This would be her right...
This would be the OP's daughter's right.
It is not the OP's right to step in unless it is welcomed.
We all know about 'the best of intentions...'