You getting in her bed is both the cause and the effect of this problem.
Because she wants you to lie down with her, any time you don't she is just going to refuse to sleep and effectively just wait until you do lie down with her. So it's making her more and more difficult at bedtime and more and more over tired.
She needs clearer boundaries.
Primarily, decide if either
(a) she is going to sleep alone. All the time. Every time.
(b) she is going to be allowed to cosleep or room share with you. Without a battle and all the time.
If (a), you need to enforce it and that will be tiring and exhausting for you. It means telling her you are not going to sleep on her room or be in her room while she goes to sleep. Ever. No matter how much she kicks off an creates, it is not going to happen.
Then for goodness sake be exceptionally consistant. She needs this boundary.
So put her to bed, tuck her in, kiss, leave. Have a mantra: "Bedtime now. You must lie down in your bed quietly at bedtime". Every time she gets up, return her.
The first few nights will be utterly horrendous. I can foresee her banging on her bedroom door, wailing, screaming to be let out. 6 years old is late to establish these boundaries, she is physically much stronger than the usual toddler that goes through this.
But if you are consistant, you should have made good progress within a week. Possibly within just a few days.
If (b), make cosleeping or room sharing less of a battle.set yourself up a perminant bed in her room. Or set her up a perminant bed in your room.
The battle is making her bedtime worse. Don't make her wonder, she need to know you eill always come into her. The battle exists right now because she's not sure. She doesn't have clear boundaries.
She needs to know and trust that you'll sleep in her room every single night. Every time. If she sleeps, if she doesn't - you'll always be there. No matter what. She needs to trust you, then the battle goes.
If she always knows you'll come into her, she'll go to sleep much easier safe in that knowledge. You will then be in a much better position to gradually withdraw her dependant on you in a kind and slow way. But to start with, she needs to trust you won't ever sneek out and leave her alone. That lack of boundaries is the problem.