Indeed. External pressures as well, as you say. But I think their difficulty will be about expectations of who you are and what the role allows you to be.
The submission of motherhood and the consort status of a prince's wife will, I suspect, be hard on Markle. And she will bridle against it, as any independent-minded, free-spirited, ambitious American would.
She will also find she is now surrounded by fake aristocratic humility and nasty back-biting. The honeymoon will soon be over. So that's going to hurt.
I hoped they would move to Canada, whence they would have found a cultural blend which might suit them. But she is set to be baptised in the church of England and to become a British subject, which concerns me some.