Hi Elsie,
It seems that - if Annie and Mary Anne Matilda are to be one and the same person - you need the death of Hector BARTLETT before the marriage to BURNS in 1899. Unless she was a bigamist!
Let me try to summarize to clarify it in my own mind.
James Alfred WILLIAMS & Mary YEO had:
*Mary Anne Elizab b 1853, d 1853 (11 weeks)
*Alfred James b 1855
*Mary Anne Elizabeth b 1858, d 1859 (1)
*Elizabeth Rebecca b 1860
*Edward Robt King b 1862
*Mary Anne Matilda b 1864
all the above b Collingwood
*Francis Peter Yeo b 1867
in Ballarat
You say there was also a daughter Ellen Sarah Florence - presumably she is the following with her mother's name indexed as YOUNG
*WILLIAMS Ellen Sarah Florence, father James Alfred, mother Mary Anne YOUNG, b 1870 in Ballarat
If I understand correctly, you have two marriage certificates for daughters of James Alfred WILLIAMS & Mary Anne YEO (is this right?).
1. Matilda YEO (b Collingwood, age 21) m Hector BARTLETT (b Collingwood, age 25), 1885
2. Annie YEO (said to be a spinster, b ?, age 34) m ? BURNS, 1899
JAP