Complex sentence: Earlier in her career, Waters made two separate attempts to be selected as a Labour candidate before joining UKIP within which she was initially chosen to stand as a candidate in the London Assembly election, 2016, but was dropped when her role in Pegida became public.
Split into simpler sentences: Earlier in her career, Waters made two separate attempts to be selected as a Labour candidate before joining UKIP. She was initially chosen to stand as a UKIP candidate in the London Assembly election, 2016, but was de-selected when her role in Pegida became public.