It sounds like you have a great sleeper and to me it doesn't sound 'broken' so I'd say stick with it! Her A times seem fairly average for a 9 week old, perhaps a little on the short side but some babies just have higher sleep needs. I would wake her to feed though. Don't worry she will extend her A times fairly quickly, I'd just enjoy the time you are getting for yourself at the moment! It's up to you if you start the day at 6 - if she won't go down again then yes you will have to - ideally you are aiming for a 12/12 day/night but if you are worried about slipping earlier and earlier you can always leave her napping for just an extra 10 mins per nap and a slightly longer catnap to extend the day a little.
With the feeding I know that my DD needs a bit of wake up time before a feed, so I let her because otherwise we end up snacking through the day. As long as you are not feeding to sleep it shouldn't become a problem.
My DD is the same and will only sleep in her cot, although I do have a lie flat pram and sometimes I will put her down in that in her room, wait for her to be asleep, cover it will a dark blanket and then I can go out! It's quite frustrating but as her A times increase you will be able to do more out and about when she is awake.
Hope that helps,
Nicolle