Well, at least Samantha isn't bragging about how much access she has to the Palace yet. I would say that would do far more damage than some disgruntled relative that hasn't had contact with Meghan in years.
And really, if we want to talk about embarrassment, I think while Meghan's half siblings are a pain with their blabbing, they aren't even close to some of the embarrassment members of the royal family has been caught in.
The half siblings seem to have very limited access and content. Tom Sykes who writes for the Daily Beast says that editors are gleeful about using the siblings to embarass Meghan. Truthfully they seem to be those relatives you only see at Christmas and assorted birthdays and then LIFE happens. They are in their 50's and have had their own life, they should allow Meghan to do the same.