" Actually, I don't see any of those things happening. You use the
proper amount of thinset or paste or mastic and the stuff will stay
where you put it and nothing will crack if it has a solid layer of
'stuff' on it. What will happen is that it will still be unlevel
and uneven, whether vinyl or ceramic. Round things will roll to the
corner when you drop them so don't drop them!

On a limited budget like she has, I still vote for mildly expensive
beautiful tile applied over uneven floors for the most bang for the
the buck"


On a limited budget, tile over sheet vinyl? You gotta be kidding.

Plus, floors that are rolling out of level on an old house that she
won't fix are the absolute worst place to put ceramic tile. Uneven
rolling floors are signs of serious movement which there is no reason
to believe isn't going to continue, unless fixed. That will crack or
pop tile. Vinyl sheet will just flex.