Sheba she has clearly said this is not about attention when it turns to requests or even perhaps demands for 'things'. It seems you want to miss interpret her words. If what the OP is saying is true then the daughter turns a heart to heart into a request for 'things'.
There may be something under the surface, maybe the OP can get to the bottom of it. But sadly this situation has maybe left everyone somewhat 'entrenched'. All feeling hurt and unhappy in their own 'corner'.
As Maryz says you need to step out of the box OP, I think.
Maybe OP you can find some way for a heart to heart that is while you are doing something together, something you both enjoy, and just ban all talk of 'buying' this or that. You can have fun or joke, you can have a heart to heart or be silent but just do whatever activity and see where it leads. Could be cooking, horse or bike riding, painting, make over session, keep fit who knows!
I've just remembered an image from the adoption training, a fountain. The jets of water are the behaviour, splashing all over the place, this is fed by the feelings and emotions of the column of water going up in the fountain. But the water comes from a reserve below, which is the needs. If you can work out what the needs are and address them, then this can effect how the child/young person's emotions are and how they feel about themselves and this will affect the behaviour.
However, of course, if there are other behavioural elements going on these need to be taken into consideration too.
And it is not a quick fix.
ODD (Oppositional Defiant Disorder) is similar to PDA but PDA is on the autistic spectrum and ODD is not (as far as I am aware). Have you looked into this?