I'm sorry, what a shock
I know how it feels, too.
I had hepatitis C (HCV) years ago - and also had it for years without knowing, and found out by chance. It was before I had children though, and I was lucky enough to have treatment and clear the virus before I had the dds.
The odds of your dd having contracted the virus during birth, or over the years since then, are very very low. If it was me, I'd probably want to tell her once I was ready (not when I"d just been diagnosed - too panicky, and there really is no rush!) so she has the option of getting tested. Its the only way to know for sure, and treatment is very good nowadays so even if she was one of the few unlucky ones, she would have an excellent chance of clearing the virus way before developing any problems.
Personally, I would a) wait till I felt settled about my own condition then b) just be honest - tell her you've had a nasty shock, and discovered you have a virus that can cause liver damage then c) let her know there is a teeny tiny chance she could have caught it from you, and should probably get tested at some point.
Before doing it, just make sure you have lots of info to hand in case she wants to ask you about it 
I personally have two friends who have had children whilst HCV+ and the children have not caught the virus. Unless Emma had cuts/abrasions AND there was a lot of your blood around during the birth, its pretty much impossible for her to have caught it then. And unless she has mixed blood with you since - open wounds, cuts, toothbrushes with bleeding gums, that kind of thing - again, very unlikely.
There is a great charity, which I think is called the HCV Trust, or Hepatitis C Trust, which will give you information, support, and people to talk to if you want them....do Google them (I'm sorry, I don't know how to do links!).
And good for you for letting others know how common - and treatable - this is. The Trust has been campaigning for years to get the profile raised, so people have the option of getting tested!