It probably was hard, because strong personal emotions are involved.
From her perspective Meghan has come along and destroyed her brotherly relationship with Harry. They used to be so close. She has seen how this effected the Queen in the last years of her life. She lives with William who has lost his brother. She is probably very angry and unable to express it.
However, it's not wrong what Meghan has done. It's quite normal for a man to marry a woman and start a new life together. Meghan is probably downright motified by the workings of the Royal Family - coming from a person who believes in equality. Why she accepted a title is double standards, which will probably reek to Kate. That Meghan hates the Royal Family has tried to undermine it and then keeps and trades of the titles.
When Meghan and Harry left the UK I thought they would disappear to Africa and set up a project to help orphans. I don't judge the life they have chosen and I hope they eventually live in privacy, peace and with fulfillment.