The more I hear about Tiara-gate, the more I think it was a fuss over the Greville Emerald kokoshnik.
It sounds like Meghan was originally going to wear the Spencer tiara, which belongs to Charles Spencer who would be more than happy to lend it. Meghan wearing the Spencer tiara instead of one from the Royal Collection would be a spit in the eye to the BRF since it would be more traditional for her to wear one belonging to the royal side of Harry's family, as opposed to his mother's family. Lord Spencer despises the BRF, and Harry's bride choosing the Spencer tiara over one from the royal vault would tickle him pink.
I am sure Lord Spencer is loyal to Crown like his ancestors before him. He was among the select group of people who attended the Queen's committal service at St George's Chapel.