The main collocation, I suppose, would be "under pressure" in US, UK, NZ, AUS, Canada etc. That's the common way to say it.
But if you want to word it slightly or use a different preposition then other ways work to. You will notice that "she's got a lot of pressure ON her" has that ON! You could not use both under AND on. Choose!
So, "she is under pressure" or "she has a lot of pressure on her" or "she has got a lot of pressure on her" (don't forget that ON!) and I'm sure somebody else out there will think of another way of saying it too! (What about "there is a lot of pressure on her" ?)