L.H.
you are not being mean... you are being firm. It does feel 'mean' , I know. Just because you love her so much..
Now, try this : I call it the 'dreamcatcher defense'.
I talked to my daughter about dreamcatchers ( and showed her mine) then I chose a certain stuffed animal from her collection and made it her personal 'bad dream catcher'.
This particular stuffed animal was a stuffed cat with wings that had jewels attached to them, so it made it easy to say the bad dreams would go through the wings and get caught on the jewels instead of going in her head. In the morning the sunlight would destroy the dream and the jewels would be re-set again. I look at this like telling her Santa is real.... just something to help her get trough the rough spot.
She was 6 when we started this. It works for the most part.
You might also want to talk to her about her 'growing brain power' and how she can control what her brain thinks , especially when it is thinking bad things. It's a sign of her growning up! She is in control of her brain!
Think of happy things when she goes to bed. It will bring happy dreams.
Other than that , you just keep being firm and putting her back in bed. I'm not saying don't give her a hug and kiss and some love, but tough love is the hardest to give.
It will pass.
Good luck to you.
I can only hope this works as well for you as it did for me.
I can't wait to read what other moms have written to you.
Have a great rest of the summer!