Hi Mich-elle, I have two boys 13 months apart. so I have some idea of what you are likely to go through. Firstly, people who say that it is like having twins are wrong - it is both better and worse than that - we have a lot of twins in my family so I do know the difference. I wont lie, it will be hard work, but you are young, and you will cope perfectly fine. i was lucky in that it was my first that was a really chilled baby, whereas it sounds like you will probably get that with your second - you don't seem to get two alike!
My advise would be to get your daughter into a good routine now - she is only 6 months old, and she does need her mummy, that's to be expected and when the new one comes along she will still be 11 months old and need her mummy - she is unlikely to be a help to you at that age - she will probably not even be walking yet. You will have two babies - a big one and little one.
Your main aim will be to keep them safe, secondly to keep them fed, clean and warm, everything else will fall into place after that.
I can tell you now that your house will be a tip, you will have bad days, but the good days massively outweigh all that and as they grow your children will bring you so much joy.
I still remember when my two started to communicate with each other as people - it was so magical.
They will grow up together and you move through the stages so quickly, before long, they are both out of nappies, they have a playmate always available and they learn from each other.
You will realise that everything doesn't need to be perfect with your second and what is important and what isn't.
The thing to remember, is that babies don't die from crying - they can and do learn to wait!