Wow Jennifer, that's a great routine for a 7 week old! I'm impressed -- but it seems like you've had lots of practice
Honestly, it seems like she's waking and sleeping for pretty long periods of time, but if she's happy and it's working for her, I really wouldn't worry about it. That's the direction she should be headed in anyway, so it seems like you just for there early. (In other words, if it ain't broke, don't fix it!)
I'm sure the long catnap is to compensate for the fact that she's awake for so long before that. I'm guessing that as she gets older and maybe some of her naps will shorten she'll probably stay up a bit longer before that and go to bed earlier. Just a guess though - like your last question I wouldn't worry much about it if it's working for you.
Everyone I know who has a LO with several older siblings says that they spend a whole lot of time watching their siblings, especially in the beginning. I think at that age my DD spent a whole lot of time staring at the wall or staring out the window, so if she's just hanging out and staring at her siblings I wouldn't worry about that either. Is your 9 year old interested in playing with her at all? (Or your 4 year old for that matter?) They might be able to entertain her once she gets a bit bigger and more interested in her surroundings.
Congrats on your new daughter! She sounds like quite an angel