There are many normal variations in poo colour - generally nothing to worry about. The main thing is, watch the baby - and use the poo as a secondary tool if there is a problem.
Generally you can't overfeed a breastfed baby and it is never the wrong thing to use the breast to comfort and settle a baby. Babies are hardwired to suck. If you tend to have an over-abundant milk supply (common in the early days)then yu might find it helps to give her the top-ups or comfort feeds on the same breast she just fed from - that way she will get a lower quantity of milk, and that might allow her to settle better. When babies suckle they release hormones in their body that help them wind down and sleep - and the cool thing is these same hormones are released in your body, making you feel tired and sleepy too.
You can tell your baby has enough milk when they wee and poo frequently - if it's come out it has to have gone in, and if they grow over time - usually 150 plus g per week after they regain their birthweight. It's not such a mystery!