At 9 weeks, I would be surprised if you needed two doublers even at night, although you never know, some babies are heavier wetter than others. Is her diaper completely saturated with pee in the morning or is there parts of it that are still dry? If there is still some dryness, I would try with just one doubler. Chances are it won't leak anyway, but if you see that it is completely saturated with pee in the morning you may want to revert to two. I never used any doubler at that age, but then DS didn't sleep more than 4 to 6 hours at a stretch when I was lucky.
If you do need the doublers, though, don't worry about how huge it looks. It usually doesn't bother the babies as much as it bothers us! And since it's only at night, you don't need to worry about the looks, if needed you can just buy bigger pajamas.
I now need to use three doublers with my son who is 21 months and sleeps for 10 to 12 hours at night. One suggestion that someone on the forum gave me was to use one of the doublers outside the diaper (held in place simply by the cover). It worked like a charm! I fold it at the front, where he needs the most absorbency, and it makes the diaper a bit less huge. So if you find that one doubler is not enough, you could always try putting one inside and one outside the diaper.
Good luck and congratulations on the cloth diapering. We use ME OS during the day as well with no leaks at all! They are wonderful diapers.