Congrats on your baby girl!!
First off I wanted to mention that for the first 5-6 weeks of life, we would try to put our baby down at like 9 pm, even for a few hours, and it would take 4 hours for her to fall asleep, crying the whole time. We realized she had severe reflux (she never spit up but had acid breath and cried after eating), and when we addressed that problem, and started her on medication, the change was a miracle, and she slept much better. I realized she was in pain, so you may want to consult with your doctor.
If it's not a physical issue, my opinion is, some babies will follow schedules, and some will not. I think it's not right to just let them cry and force them into our schedule since at 8 weeks their stomach is small and needs to be filled frequently, but obviously you'll hear a thousand different opinions about that. I think if they cry and cry, eventually they will fit into your schedule, but it would've happened anyway at that time, and why put her and you through that trauma, and you won't sleep anyway. If you can follow a GENERAL structure, like feeding about every 3 hours, that will help, and gradually that time will lengthen at night. And, we did cluster feedings in the afternoon/evening, which did help a bit.
I have a 6 month old. At 8 weeks, my baby still woke every 2-4 hours to be fed, and I know she was hungry, because she would inhale the bottle (which was bottled breastmilk), and go back to sleep. She also had severe reflux, so I had to hold her up for 1/2 hour after each feeding.
I also had to go back to work at 12 weeks, and was nervous, but it just seemed to fall into place, and my job is very mentally and physically challenging. I was still up every night pumping/feeding for like 2 hours on/off in the middle of the night for my first month or so back to work, but my body adjusted, and while I was tired, I usually didn't feel like I'd collapse, I could handle it, and I'm 41 and out of shape.
What helped was that my husband and I shared the night feedings. So, he'd do an extra feeding if I had to work the next day, and I'd do an extra feeding if he was working the next day (we each work 30 hours a week and split taking care of her). If you breastfeed, maybe you could pump like I did, so your husband would have a bottle for her. Unfortunately, parenthood equals sleep deprivation early on. I know it can be so frustrating, but a lot will change in the next month, and you'll realize that gradually it will get better.
We tried baby whisperer and babywise, but it just didn't work for our baby, we gave up since it was just stressing everyone out. But, you need to do what's right for you. We followed our baby's signals for when she was tired and when she was hungry, and now it's paid off. She sleeps 10 to 12 hours through the night, in her crib, but those first 3-4 months were so exhausting. But, when you're sitting there feeding her in the middle of the night, thinking about how exhausted you are, and will be at work, just look down and cherish the moment, it's likely you'll miss it. I did that, and suddenly I felt less frustrated.
And yes, I agree with everyone else. Her sleep schedule will change a lot, so just be prepared for that.