Not too soon from a time point of view BUT...
what she enjoyed in October when the crowds are relatively light may not be so much fun at Christmas. The place definitely is gorgeous, BUT the crowds can be horrendous.
The first time I took DS to WDW was between Christmas and New Years. (The company I worked for was having a meeting beginning Jan 2, and had told folks to bring families if they wished - we got in Dec 30th). Well, we survived New Years Eve at Epcot, and it was awesome. The next day was another thing. My DS, then 7, ASKED TO LEAVE THE PARK. It literally was so crowded that he was overwhlmed and could not enjoy it.
On the up side, we knew we had only seen a fraction, so planned another trip the following summer (and many trips since).
It truly is a magical place with a child and we have many wonderful memories. Just be aware it may not be the same experience for her that it was in October.