While I guess Eugenie (and also Beatrice in future) will wear the York tiara as I mentioned before, I also think it'll be great for them to use Q Mary's Fringe tiara to continue the tradition of British princess wearing it in their wedding day. The Strathmore Rose tiara, which was a gift to the Duchess of York, is a good choice too (if it's in a good condition). If her grandma plans to loan her something, I think it will be the Fringe or Strathmore Rose (but it also depends on what Meghan wear, if she is given these two (it's unlikely for the Fringe I believe) then of course we won't see it on the Yorks, they have no reason to repeat wedding tiara in same generation I guess?