It's handy that indigo quoted an earlier thread, so I don't have to repeat myself as much here.
I and one of our children each skipped fourth (I moved from third to fourth mid-year, and our child skipped into fifth on a school change). In both cases, the skip was into a multi-age classroom: I finished the year in a 4/5 combination, then went to a 5/6 combination the following year, and our child started the new school year in a 5/6/7 combination. The transition was successful, on balance, for each person, but I think whether yours will be as suitable depends greatly on the individual child, and the makeup of the receiving classroom and teacher. FWIW, I was quite shy as a child, while our child is pretty much the exact opposite.
And yes, this did, in combination with a few other skips, result in my entering college on the young side. We have not yet decided whether our child will enter college early, although if it seems appropriate at the time, that will definitely be an option. If your child is not ready for college, as a complete package, after high school, you can always do a gap year, have her take a course or two while exploring any special non-academic interests she has, experience the world of minimum wage jobs (not a bad life lesson, there), volunteer, etc. A grade skip now does not commit you to early college later.
