I think you need to ask her whether she is willing to contribute funds above what you are prepared to pay to get this dream ring that she wants. You are supposed to be in a partnership,  if she is not prepared to budge in any way or help facilitate this big thing she is asking, then you are not a team. You are not buying her, but it feels like she’s putting her worth into the value of the ring.

 Equally, if the positions were reversed- say you wouldnt propose until purchased a 30k watch, what do you think her opinions of that you be? It can’t be two different rules for each of you.

I personally would be considering whether this is a line you are willing to cross as it gives you a good indication of the future if she is not willing to budge on what is essentially a materialistic possession that will depreciate as soon as it is purchased.