At the Street Child's tenth anniversary party at Kensington Palace, the mum-of-two gave a passionate speech.
"I was never more proud to see my tall, beautiful, upstanding daughter full of courage."
"She had scoliosis. In other countries in the world she would be put in an asylum and locked up."
The 59-year-old also praised her son-in-law Jack Brooksbank for "trying to tame the lion, which is my daughter."
Eugenie took to Instagram about the charity.
Posting a photo with her husband, she wrote: "There are 121 million school-aged children around the world who are not in education. Jack and I were proud to support @streetchilduk and my mum who’s the founder patron, as a global ambassador. Congratulations @sarahferguson15 for all your hard work. Please support the #countmein campaign - give before 21st February 2019 and public donations will be matched by the UK Government."