Been mentioned a few times
Highly unlikely even if it hadn't been on tour, that Meghan would wear the same wedding tiara. Unlike Kate, she is likely to wear the same tiara for some time to come. Having the one associated with Kate's wedding day, would seem an unlikely pick.
A lot of girls don't dream of being a princess beyond kindergarten.
You don't need a dress covered in lace or bling for a major tiara. Actually the opposite would almost be true. The simpler the gown she chose, the more impressive a tiara might be called for. To make a statement and have the presence in the church.