Have you moved houses or to a new town or even moved her into a new bedroom recently? If so, this can cause a trigger on getting her to sleep.
Does Daddy stick with Mommy/s scheduling with regards to going to bed or does he play with her making it even more difficult for her to go to sleep because after playing, her mind is wired up. It's what I've always referred to as the barmaid syndrome, not that your baby is in any way associated with bar rooms or anything...
Back when I was working as a barmaid 6 nights a week, I'd come home around 4am to 5am & literally be so wired up from working that I wasn't able to actually lay down let alone go to sleep so a few friends and I got into the habit of stopping off an an all-night diner where we'd get a bite to eat and sort of BS around until the buzz of working a busy night wore off and then we could actually go home and rest although for me 99.8% of the time it was go home, shower, get 10mins of rest, pick up my daughter from her night sitter, change her into day clothes, unless the sitter did it for me, which she did much of the time, and I would take her to the daytime sitter that allowed me to work full time during the day in a factory. After working 10 to generally 12 hours shifts at the factory, I was back picking up my child, spending a total of about 2 hours with her, which usually included a bath, washing a few clothes, repacking her bag, and picking out clothing for the next day with extras in case she made a mess on her first outfit then took her back to the night-time sitter before I headed off to work as a barmaid again where afterward, I was once again too wired to go home and sleep. My ex refused to pay support and this was during the time before the opening of the Child Support Enforcement Program so I had to work 2 and 3 and even sometimes 4 jobs in order to keep a roof over our house and food on the table as well as covering for health insurance through the factory job, which also had short-term and long-term disability as long as I worked at the company and I had worked my way up into the Quality Control Program where we all met to find safer ways to do the same job that would lower the rate of accidents.... It was quite an honor and each time we met outside of company hours we rec'd payment for it.
It took forever after I was able to scale back my hours of work because my daughter, quite honestly, didn't really know the real me or rather the person to put her to bed, gave her a bath every night, cooked every night, etc... because I was working all the time. We did get through it.
I would put her to bed. If she got up, she was put back in bed. If she got up again, she went back to her bed. I kept this cycle up for about 3 to 5 nights before she got the picture that it was nighttime and she was going to go to bed no questions asked. It just takes perseverance on your part.
At 8 mos, I'd cut out all naps. There is no reason for her to be taking a nap at 8mos old.
Don't let her pull the, "I wanna sleep with you" stunt either b/c it will become an every night thing and make it even more difficult to break.
Cut out everything except a glass of water after 5-6pm. The sugar levels in drinks other than water will cause your child to become hyper. It's like feeding the lion and that's the last thing you want to do. Try warm milk with a touch of vanilla in it. Stay way from chocolate.
If you stick to the schedule then she should be sleeping at night on time every night without any problems and then you can sleep at night too.
Hope this helps... b/c I've been there and done that.