Its hard to fight the family always trying to tell you whats best. Stay strong with it. You know what is best for her.
I b/f my son until he was about 6 months. I would have gone longer but my milk started to dry. At that time I had raw goat milk available to me so he drank only that 50/50 with distilled water. I put 1 dropper of baby calm and a drop of oregano/safflower in every bottle he every had. He did drink a lot of milk! I started him on just fruits around 7 months and very slowly worked our way up to more. He hasn't had any milk at all since about 18 months though.
Also, I know it is hard with her still being up so much at night. Stick with it. Mine didn't sleep all the way through the night until he was over a year old! Some are just lucky.
Try improving your diet and follow MH's advice for herbs to take while bf to improve your milk as much as possible. Remember, whatever goes in you, goes in her too.