Hi, Debbi, Disney Resort guests can use Extra Magic Hours even if they do not have a travel package that includes park tickets. So, YES, your daughter can participate in Extra Magic Hours, but you will need to add her to your room reservation so she can receive a Key to the World card at check-in which serves as your Resort Identification. A Key to the World card must presented by each person in your travel party during Extra Magic Hours. (You will not need to purchase additional park tickets for her if you already purchased them in some other way.)
What you will need to do is call (407)W-DISNEY, have your resort confirmation number handy, and ask to modify a resort reservation. Simply add your daughter's name to your reservation. If all 5 people in your family are ages 3 and older, you may have to switch your resort option as some rooms can only accommodate 4 guests.
Click here to read about rooms for 5 or more guests, or you can do 2 connecting rooms. One of my favorite options is a room at Port Orleans Riverside that has a trundle bed and allows the 5th guest.
Have a wonderful July vacation!