Reddit mentions of Classical Ballet Technique

Classical Ballet Technique by Gretchen Ward Warren sounds like everything your sister is looking for.

Classical Ballet Technique https://www.amazon.com/Classical-Ballet-Technique-Gretchen-Warren/dp/0813009456
I've had this one for years. I liked it a lot, especially when I first started. It has a lot of pictures and details. It's more of a coffee table book size, definitely can't keep that in your dance bag!

I also second the recommendation for Gail Grant's Technical Manual and Dictionary
https://www.amazon.com/Technical-Manual-Dictionary-Classical-Ballet/dp/0486218430/ref=pd_lpo_sbs_14_img_0?_encoding=UTF8&psc=1&refRID=4325M8ZFCY5EHDJ6N826

Classical Ballet Technique, by Gretchen Warren. It has step-by-step breakdowns (with photos of professional dancers from the late 80s) of everything from plies to ballet running.

Back On Point has some good inspiration and workout plans. Its all geared towards getting 'back on pointe'. Somewhere on there she also posted a daily workout with different exercises... I'll have to dig around for the links later. I've found it pretty helpful :D



Also look into these:

• New York City Ballet DVD
  
• Perfect Pointe Book
  
• Classical Ballet Technique
  
  HTH!