No, she's not slow. She is just fine for her age. In fact, pushing her can make things worse not only now but later when she is in school. I used to do workbooks with my son (will be 4 in May) and he stopped listening to me, wouldn't follow instruction, etc. He was bored with me. He was already home with me all day telling him what to do-pick up your toys, eat your lunch, time for a nap, etc that he didn't want me telling him what the directions were in the books. I signed him up for a part day program (3 hrs a day 5 days a week) and he is learning so much so fast that it makes my head spin!! He wants to learn there because it's with other kids his age and 2 teachers he doesn't have to look at all day like he does mommy!!
Save the writing for Pre K/ kindergarten. Work on recognizing shapes, colors, number, letters, etc. Make it fun and follow her lead in it all. If she really wants to write letters. Try dashing them out on paper and letting her trace them first. She could see and E the opposite way that it really is right now because their brains are still trying to learn it all.