After a young heiress unleashes primal powers, she is visited by a mysterious stranger and learns she must take on interdimensional beings that want her dead.

I get now where I should be going with this. Thanks so much for your help!

Let's slot your words into the revised logline and see what happens:

A spoiled [???] heiress discovers she can manipulate the energy flowing through all things. Now interdimensional beings want her dead.?

I left the "spoiled" placeholder, because you do need some intrigue about the protag's inner struggle or circumstances.

The LL still feels somewhat truncated. Needs a bit more. A ticking clock, and obstacle, a hinted-at twist... something...

"... Now interdimensional beings want her dead but..."
"... want her dead and..."
"... want her dead before..."

As is, the revised LL tips too far toward passive for the protag. What's she plan to do with those powers?

But as is, the LL establishes an unusual and intriguing conflict. I mean, wow, those are some massively expansive and powerful elements you're playing with.

She's supposed to be unleashing the primal powers from within. The kind of powers that will enable her to manipulate the energy that flows through all things. How can I show this in the logline?

I think you're correct to leave out Mysterious Stranger.

Thanks!