Thirst for learning question

I've read a bunch of Nancy's posts but haven't found the information I wanted so here I go with a new thread. Please direct me if this has been discussed on another thread. My 4.5 year old seems to be learning things leaps and bounds to the point that I am having difficulty keeping up with her! I don't push but try to go at her pace and/or limit things for her. One of my biggest fears is becoming a pushy parent but I'm not sure where to go with her. For example...she has known her letters and letter sounds for well over a year. About a 10 months to a year ago she started putting sounds together to read words. She was trying to read large adverts in the newspaper so I directed her with simple 3 and 4 letter words. I would do words with her when she asked but didn't push it. Then she didn't ask for a while. Now we are back to wanting to do words so we started looking at site words. We practice the words she knows and then were adding 2, maybe 3 new words but it went so quickly for her we started doing words until she lost interest or we had a word or two that she struggled with. She now knows about 50 site words. We rearrange the words she knows to make sentences and she is reading beginning reader books. She will start kindergarten next summer (school is year round here) and doesn't seem bored with preschool though they are learning letters, letter sounds, days of the week, months of the year etc. all of which she already knows. So, do I keep letting her learn at her pace, try to slow her down, redirect to learning about other things? I hope (only so many slots available) to enroll her in Spanish Immersion when she enters kindergarten, partly because it is something I can do for her culturally and mainly because I'm worried she will be bored in a traditional class.