Re: STTN at 8 weeks
Yes, you can safely let her sleep. She'll make up for what she's missing at night with her daytime feedings, and your supply will adjust so that you make more milk during the day and less at night, when it's not needed. If your LO starts waking again- and she probably will- she'll quickly boost your supply back up with her increased demand.
Just one thing to note: consistently going long stretches (6 hours or more) without nursing increases the odds that your fertility will return. If you've been relying on breastfeeding for contraception, you can no longer consider that to be providing effective protection.
Coolest thing my big girl said recently: "How can you tell the world is moving when you are standing on it?"
Coolest thing my little girl sang recently: "I love dat one-two pupples!"