Sweden has a jewel foundation,no? There's no reason to give Sophia a tiara. She will just select from what is left after the others make their choice
There is two jewelry foundations actually Plus that the Kind owns some tiaras himself.
And I don't think it is that easy that she can pick up what's left. You're right can't be given any of the tiaras in the foundations, but she will still have an potential access to all tiaras. I hardly think that they stand in line (in rank) and choose tiaras I think it's a chill discussion and decision among the Royal ladies. On the other hand there are special tiaras reserved for the Queen, and those who could be seen as reserved for the Crown Princess, but I actually don't think that the Crown Princess would mind to share one of "her" tiaras once.
When it comes to the wedding and her wedding tiara, she will most probably be first in line to choose tiara. The desicion which tiaras she will wear will be will discussed with Sofia and the King and Queen (and maybe Carl Philip).