Compromise is always good. Just set the rules up front.. I agree with letting her wear the pink snap pantry over her big girl panties, but only to play.. not to go potty in..
Tell her if she potties in them, that they are too old to wash so they will need to be thrown away (and then if she potties in them do it).. also explain to her tell her that diapers are expensive, so you cannot waste them..
It is a phase.. I am sending you strength..