the child is learning

*note-I can't get the font to fix itself, where the second half of the post isn't in caps, it's really weird. I swear I'm not "yelling" though*

Occasionally I get a little freaking out by Molly and what she's doing. Lately she is just taking off and I can visibly see her making connections and growing and it's crazy. She started sounding out words sometime in November, so 7 months ago. She is now reading on a first grade level and beyond. Tonight she read the first two verses of "My Shadow," a poem by Robert Louis Stevenson. She needed help on just a few words and I think if it had been earlier in the day she would've needed help with even less than she did, she always has more trouble when she's tired, but she wanted to read so we went with it.

This is what she read:

I have a little shadow that goes in and out with me,
And what can be the use of him is more than I can see.
He is very, very like me from the heels up to the head;
And I see him jump before me, when I jump into my bed. 

The funniest thing about him is the way he likes to grow--
Not at all like proper children, which is always very slow;
For he sometimes shoots up taller like an india-rubber ball,
And he sometimes goes so little that there's none of him at all. 

The words in bold are the ones she needed help with. I'm just astounded that she figured out "proper children" all by herself. My child is three...three. She'll be four in a little over a week, but still, it's crazy. 
The Singapore kindergarten math book we have we can go through ten pages at a time because it's all really easy for her. We're still going through it though, because I think laying the ground work and practicing basics is important. To work on her level we've been doing basic addition and subtraction with objects, like beads. We've been doing problems like 17-9=... She counts out 17 beads and then takes 9 away so she can see how many are left. We've also been working on memorizing addition facts since that is an important skill. She's got all the zeros, 1+0, 2+0... and she's just about got the ones. Seems very simple, but still, are kids her age supposed to be able to do that? It leaves me a little baffled. 
What do I do with her? I mean I know, I'll just keep doing what I'm doing, following her lead and giving her what she asks for, but is that enough? I feel confused.