Can I Gust between two Dianas and Ravenbloom triggers?

Both Dianas trigger simultaneously — the turn player adds theirs first, so the chain resolves Ravenbloom, then the non-turn player's Diana, then the turn player's Diana. You can Gust before each Diana trigger resolves, but not after the combat showdown starts unless before that trigger resolves. Diana need not be on board for her trigger to resolve.