If you want her for showing or breeding, then if there is any opportunity to get her onto a ewe (of any variety), then do it. They
always do best on a real ewe.
And I've fostered lambs that've been on the bottle for longer than 6 days, so that's not necessarily a problem.
However, if you can't get her fostered, then 'formula'. Many on here say goats milk is as good, if you can get it - just make sure it's raw, untreated. Cow's milk is not as good; I can rear lambs on my Jerseys' milk, but Jersey milk is a special case. And they do need more of it than they would of sheep's milk.
I start mine on every 2-4 hours for the first 24 hours, then every 4 hours for a few days, then 4 feeds a day. I don't get up in the night after the first few days, lambing time is busy enough. They get their last feed when I go to bed and their first as I get up. (I'm sure it
is better for them to have smaller, more frequent feeds for a couple of weeks, so if you have the time and energy and want her as a show/breeding sheep, then by all means do that.)
I always follow the guidelines on the ewe milk powder pack in terms of quantity per day, but generally don't wean quite so soon. I find 6-8 weeks is plenty young enough to wean and I don't attempt to wean them unless they're eating creep well. Some people seem to get a lot of problems with bloat if they keep bottle-feeding once the lambs are eating cake, and others keep all orphan lambs away from grass certainly until they're weaned (and some people never let them onto grass) but have a read of
this post by jaykay about how bloat can happen - so long as you are scrupulous with hygiene of milk and bottles (and troughs) and don't let them have too much of any one thing at any one time, you should be fine.
Good luck !