She was one of 27 riders from around the UK who followed in the hoof prints of Genghis Khan on the charity's 200km trek and camping trip across the vast plains and remote valleys of the Khangai Mountains in Mongolia.
The challenge that ended in Kharkhorin, once the historic centre of Genghis Khan's Mongol Empire, was one of the fundraising activities being organised by the Brooke to commemorate its 75th anniversary year.
Jeannine, who stables her own horse near Hailsham and has previously done fundraising rides for the Brooke in Egypt, India and Jordan, said, "This was the most challenging for all kinds of reasons. 0The majority of our luggage, including tents, was stranded at Moscow airport for three days and the weather was much wetter and colder than expected.
"But overall it was an absolutely fantastic experience and one I wouldn't have wanted to miss.
"We rode native Mongolian horses that are very small but also very strong for their size. In a country that is three times the size of France, but with a population of only just over two million, the wide open spaces were incredible.
"We trekked across vast landscapes and for days only saw nomadic tribes and herds of wild horses, yaks, goats and sheep that provide these families with self-sustaining lifestyles.
"It really was an unforgettable trip and I'd like to thank everyone who has sponsored me for their generous support.
"It was pretty tough spending up to six hours in the saddle and then camping at night, but a drop or two of the local vodka turned out to be a bit of a cure all in helping to ease aches and pains and help with insomnia during some of the very cold nights."
Jeannine is nearing her target of raising £3,000 for the Brooke, which helps working equines in some of the world's poorest communities.
And she has already set her sights on her next fundraising expedition for the charity, taking part in the BUPA Great South Run in October.
Anyone who would like to help Jeannine meet her fundraising target can visit her charity web page at www.justgiving.com/jeanninewilliamson or contact her on 641078.