The 65 year old stars in U.K. drama Wild At Heart, and scenes for the show are filmed on a nature reserve in South Africa.
Mills took time out from the shoot to explore the area, but she was caught in a dangerous situation when she encountered wild beasts.
The Golden Globe-winning actress tells the Daily Express, "I decided to walk to the lake to see the hippos. As I got closer two huge hippos heaved out of the water towards me.
"I ran as quickly as I could up the hill and as I reached the top an elephant came charging at me. I leapt on to a trailer to get out of the way and it was full of manure."