Complex sentence: Atlantic jewel (foaled 26th December 2008) is an australian thoroughbred racehorse, so far undefeated, she is considered the best 3yo filly in Australia.
Split into simpler sentences: Atlantic Jewel (foaled 26th December 2008) is an Australian thoroughbred racehorse. So far undefeated, she is considered the best 3 year-old filly in Australia.