She could be feeling a little anxious about something or just going through a change. She just needs the emotional comfort right now. Totally normal.
You could try starting the bedtime routine a little earlier than usual so that you can include a little more of that special time. Let her know that you are doing that and that the routine tonight will include an extra book or a song together or something else that she would like. Let her know ahead of time what to expect, "After bath we're going to brush teeth, read 3 books, not just 2, sing a song, say goodnight (with hugs and kisses) and go to sleep." That way there are no surprises and she is prepared for what will happen.
My 6 year old likes to try and negotiate, but when I let him know what's going to happen, even if he doesn't love it, he can accept it. It's when I change something at the last minute (and we all have to do that sometimes) that he gets upset.
If she's really tired (like too tired), you might need to put her to bed earlier. Maybe she's going through a growth spurt and needs extra sleep. But it kind of sounds like she just needs a little extra reassurance.
Good luck!