I suggest that part of the problem is that she's overly tired. Put her down for a nap at a regular time everyday and at a time when she is not very tired. She still needs naps at 8 mos. Make them a part of her daily routine.
Lay her down atnearly the same time every day. To start with watch to see when she first starts getting just a little tired. That's the time to lay her down. Don't hold her, since she wakes up when you lay her down. Put her in her crib. Pat her back, talk warmly with her as you tell her it's nap time and leave the room. Let her cry no more than 5 minutes. Go back in pat her on the back to let her know you are still around, leave. Do this several times extending the length of time in between going back in.
She cries for 3 possible reasons. The obvious one is that it's worked to get you involved and allows her to not nap. Then the more tired she becomes the more difficult it is for her to go to sleep. The more worked up she gets it becomes impossible to go to sleep. Which is the second reason she may not be falling asleep. Even adults have trouble getting to sleep if they're overly tired and if they're upset.
The third reason is related to letting her cry it out. Not only does she become too tired and upset to sleep until she's completely worn out she still does not have object constancy. If she can't see you, you don't exist in her immature mind. When you lay her down, you're going away and she is frightened.
Her jumping up and down indicates to me the possibility that she is not only too tired but also that she is frustrated. She doesn't know what to do. She knows she wants you but you keep disappearing. She knows she's very tired but can't calm herself down. She needs you to teach her how to calm herself. And she can only learn that before she's so tired and upset.
When you go back in and pat her back and say soothing words to her you are letting her know that you understand her need as well as showing her that she can calm down.
Playing soft music may also help. Music is soothing.
An overly tired baby can rarely get easily to sleep. You have to find the time to put her down when she is just a little tired or have the same time everyday so that it is routine for her. You have to be consistent. YOu have to teach her how to calm herself. And you have to be persistent. Being still awake after 12 hours sounds to me that you allowed her to stay up.
I think your situation is an example of how "cry it out" does not work for many babies. A baby needs a sense of security so that they can sleep. When mom and dad abandon her she gets frantic. She doesn't know you just in the next room. I am a firm believer that we parents need to respond to our babies and children's distress. Yes, they can manipulate us with tears but at 8 months they are not manipulating. They are letting you know that they are in emotional pain.
A note on manipulation. Manipulation is getting someone else to do what we want them to do. We want the baby to go to sleep. When we leave them to cry for 2 hours they are not sleeping and neither are we. How does that help anyone. Now if they cried and we picked them up and played with them then they could be said to be manipulating us. But when we go in, show them how to soothe themselves while leaving them in bed we are teaching them how to get to sleep. We are helping them to do what we want them to do. They have not manipulated us.
Try this consistently for a week or two and I think that she'll be back to napping. At 8 mos. she may need a nap in the morning and in the afternoon. It is imperative that you start the nap routine before she is exhausted.