There has to be an adult with her, for sure, and since it's rated R there's the usual partial nudity and inappropriate content. It's certainly happened before in this cast. I would say the following about the beloved Austin cast, in reference to your question:
*People will likely be WAY less clothed than in the movie. And since it's running around a theatre, she'll see the full effect. I mean older men in lingerie and women with duct tape over their nipples. If you're cool with that, then sure!
*There's lots of screaming cuss words and profanities and possibly disturbing jokes (the clothes hanger one always gets me) that you may or may not want her to hear.
*Alcohol. It's there. On that note, you may even want to check with the Drafthouse on their kid policies since I haven't been there in awhile, but as I recall, I've seen younger kids come in accompanied by an adult/family member before.
With all that in mind, it's up to you. I may wait 'til the 15th birthday, but that's just me. I know kids are exposed to just about everything anyways and sometimes introducing the fun in a good way is good too
Hope that helps answer your question! (In case you wonder, I played in Queerios for years and come visit, but teach middle school now too. You'll make it an awesome time, I'm sure