8 Month Old Sudden Nightwakings

She could be sick.
She could be getting her teeth (the start of teething) so I would buy some
Baby Orajel (it's topical & you put it on her gums).
Also, get baby Tylenol to give her when she gets up as she could be
starting to teeth but you can't see the teeth starting to surface yet.
Also, be sure she is not too hot or cold.
A big also............she could be hungry. Does she breastfeed or take a
bottle? If so, I'd try feeding her quietly in THAT room w/o turning on the
light, holding her afterwards for a few mins then gently so as not to wake
her put her back into her crib.
Work WITH this stage trying different things I've mentioned above & you
will soon be back on track with her sleep patterns.
But I'd definitely pick her up & try soothing her w/a nighttime feeding and/or medicine for teething!

All kids go through phases where they wake up hungry. Feed her and she'll go back to sleep. She is about to have a growth spurt. She'll do this again, big time, at about 18/20 months for a few weeks.

8 months is a huge sleep change stage. I would continue what you are doing and it will pass. I personally did the back pat thing. I think big problems come when you take them out of the crib and either carry them around to sleep, rock them to sleep, or turn on the TV. Believe me that I have friends that have done all three!

2 things made for night wakings at that age with my kids.
1) growth spurt. One of mine suddenly hit a growth spurt where he needed more food. Once I started really stuffing him full of oatmeal cereal before bed, he started sleeping again.
2) one of mine suddenly became afraid of a stuffed animal that was in his room at night. It had been in his room since birth - it wasn't new. And he wasn't afraid of it during the day. But it must have looked different to him at night, because suddenly, right around 8 or 9 months, he would wake up crying in the night and wouldn't go back to sleep. One day, on a total whim, I moved the stuffed giraffe to a spot where he couldn't see it from him crib - and he stopped crying at night.

We experienced sleep pattern changes near any milestone" and I think crawling & pulling up is a milestone.
Yes, it was around this time we caved & started driving ours around to get him back to sleep. BAD move!!! Lol
Sounds like you're doing the right thing.
You might want to try some soft music on "repeat" all night so it's not so stark and lonely feeling when she wakes up. She might surprise you & go back on her own.

Babies go through so many phases in that first year of life. They are changing constantly. Just when you think you have a routine down, bam!, they change it on you.

I wouldn't worry about developing a habit. She's going to change again in a few weeks or a month, so it's really not going to affect (effect?) her.

We always went to our kids in the middle of the night. Sometimes all they need it to know that we are still there and we will come if they call. If she's going right back to sleep after being comforted by you, it shows that she feels better just knowing you're there.

Our kids are a little older now (6 & 4), and occasionally they still need us at night. It really is so rare, but we get up if they call. Sometimes they need this extra thing from Mommy or Daddy in order to feel safe and secure and be able to get back to sleep.

Keep going to her. She's not manipulating you (she's far too young to do that). She really needs you. I think you'll find she will settle back into a routine of more sleep if you comfort her now. And years from now I don't think you'll regret being there for her when she needed you.