Your dd is still too young for solids and frankly, they won't help. I know a lot of people (usually older relatives) swear it works, but don't hold your breathe. Besides, you're doing an awesome job exclusively bfing. We had to supplment and, despite what some might suggest, formula doesn't make them sleep any better in the long run either.
Crying it out is also not always a viable option. I know other peoople will swear by this one as well; however, even Dr Ferber (who originated the technique) says that it should only be used as a last resort and the child should not be left to cry for long. If the child continues to cry, the underlying issue must be addressed. Also, I think he advises this only for older babies. I know the feeling where you just want to close the door and walk away for 8 hours, but your child is still very very young.
It may not yet be physically feasible for her to sleep as long as you (an adult) would like. Her tummy is the size of her fist and not able to hold that much yet. Breast milk also is digested much more efficiently and is far far better for her in the long run than formula.
All I can say is that babies will only adhere to their own schedule and you may spin cycles and become more frustrated trying to get her to adhere to your own schedule. She may also be, like my son, a "bad" sleeper. My son would only sleep in the same room with us and would wake every 3 hours until 18 months even after introducing foods! (consider yourself lucky btw)! I tried the cio thing (horrible failure and set us back big time). We tried everything that was supposed to work. Every baby is different and w what may have worked with one will be a total failure with another.
He's finally sleeping through the night, and yours will too. I felt really guilty at first about him sleeping with us since it was the "wrong"thing, but you know what? We ended up sleeping. I could just roll over to nurse. I told my OB and her response was, "My 3rd was like that too. You do what you have to do to get some sleep." There is no wrong way if it works for you. So if the bouncy seat works, that's better than nothing.
There is one book I'd recommend you look at. To me, it was the most helpful for understanding my son's sleep and had the best suggestions for us. It's Elizabeth Pantley's book: No Cry Sleep Solution. There's also a Yahoo group for people using the techniques. She presents a lot of scientific data and study results that pretty much poke holes in the sleeping through the night thing. (did you know that Dr's consider sleeping through the night to be only about 6 hours?)
Sorry if I didn't give you the answer you wanted. I just thought I'd share my story to give anothe perspective. I've always heard that kids are either good sleepers or good eaters but rarely, if ever, both. I know that's been the case with us and it's actually a pretty good thing. I also personally believe that the people who say their little babies are sleeping through the night are probably either lying or are so sleep deprived themselves that they're just not doing the math right.
As a friend of mine said: The days are short and the nights are so long. In the scheme of things, this time with them is so short. They'll be sleeping through the night/on their own/ in their own bed/etc before you know it.