"He says his mother's sisters had earlier offered Meghan one of the
Princess of Wales's tiaras."
The Spencer tiara isn't theirs to offer. It belongs to Charles Spencer, who told Harry three times not to marry Smegz. Any other tiara that Diana wore belongs to The Queen (and as we have said before the only other one she really wore was the Lover's Knot on permanent loan to Catherine - I can't find pictures of her in other tiara. Necklace headbands, yes, but not other tiaras)
ETA: It claims that she was offered an emerald and an aquamarine tiara. And the Queen said "Tiaras suit you" (but never let her wear one again and did not give her one on permanent loan) and then everyone clapped and thanked her for her service. SURE...this happened