Which "new" tiara will she choose next time?
IMHO, I think Sofia will stick within what she has already worn; perhaps adding in the Diamond Bandeau or the larger Cut Steel Tiara. Again, IMO, it's tragic that she's been given access to any of the Bernadotte jewels but if you look at what 'ol Sof has worn already, she hasn't worn any of the "good" tiaras. The Amethyst Tiara is the only one that really has anything going for it and at the same time, Silvia, Vic and Madeleine haven't recently worn it. So, it's kind of like a "meh" situation. It sucks she can wear it but if Silvia, Vic and Madeleine don't want it then, meh.
Other than that, here is what I think. Sofia obviously doesn't have access to the Queen's tiaras; no Branganza, Modern Sapphire or Nine Prong. Vic's Baden Fringe is closely aligned with her and is meant for Crown Princesses only. I would be shocked and floored if the Baden Fringe ever appeared on Sofia's head when even Madeleine has never worn it. She also can't access any of the personally owned tiaras so that knocks out Lilian's Laurel Wreath, the 18th birthday tiaras of Vic and Madeleine and Madeleine's Modern Fringe. The Cameo isn't Sofia's style and she would never go for it. (Side note, could you imagine the Cameo on Sofia? I cannot think of anything more funny. Her forehead would be even bigger and it would just keep going because of the height of the Cameo.) Finally, I highly doubt Margaretha would ever let Sofia wear her gorgeous Aquamarine Kokoshnik.
I also don't think that Sofia will wear any tiara that Silvia still actively wears. That said, I think the Connaught is safe. It's one thing for Silvia's blood daughter's to wear a tiara that she still wears but a married in one that you never approved of in the first place and is the lowest on the totem pole? I certainly hope not simply for Silvia's sake. She's a Queen and she shouldn't be sharing a tiara with a married in royal. Silvia is also the only one who wears that ruby tiara and does so only occasionally - with the history behind it, I'm not surprised. Sofia won't be getting her hands on that one either.