I agree with everything Dana said.
I would also add that even if it seems she's not getting a lot at night, you may not really know. My son nursed 20 minutes at a time when he was a newborn, and he now nursed 5-7 minutes max (he's one), but I know he's still getting a lot, he's just more efficient. I also never felt my milk let down.
Also, if she doesn't get a lot at night, she'll compensate in the morning. And if you're that full in the morning, she may be getting her biggest feeding then. The same is true if you miss a feeding due to her napping or something. It just means she'll take more at another nursing that day if she needs it.
I have also read some recent studies about beer helping increase production. If you're worried about the alcohol, what I read said alcohol-free beer has the same benefits. Drinking a lot of water helps, and not stressing does too! You can also pump directly after your nighttime nursing to increase your supply in the evening. However, if she's gaining weight, then I really think you're doing fine.
Your baby will get what she needs. And even if she only gets a little at the night nursing, she's still getting the comfort and care you're offering her to help her fall asleep. Sometimes nursing is more about comfort and bonding than nutrition.