Seem to have been a lot of 'fibs' told by both Mabel and her mother. Mabel clearly not married to a Gordon when she had Bertrude, nor was her maiden name Armstrong.
As already stated, Mabel Gordon Broman birth Mar.qtr.1889 - however, her mmn was given as Armstrong but that's a fib too as should have been Bull.
Going further back - Margaret Bull married John Armstrong Dec.qtr.1865 Isle of Wight - she would only have been 16 as her birth was in Dec.qtr.1849!!
Her husband was a soldier and a son baptised 1871:
Ffolliotte Charles Armstrong bp.19/4/1871 Allahabad, Bengal, India son of John Charles Armstrong and Margaret. (He appears to have reversed his names as an adult).
Daughter Ivy's birth already posted - born in Ireland and mmn Bull.
Son George W. is said to have been born in Jersey.
Then comes Mabel born after Margaret had married Alfred J. Broman in 1888. Correctly registered as Broman although mmn wrong i.e. not Armstrong. She was baptised as Mabel Warren (?) Broman 4/6/1889 Carisbrooke, da. of Alfred and Margaret. Unfortunately, I can only view a transcription so 'Warren' may well have been incorrectly transcribed.
In 1891 Alfred shown as married but Margaret not with him (with a dau. Bessie and her child). She is listed on Ancestry as Margaret Brooman, married, with her 4 children but Mabel listed like the others as Armstrong!!
Later Margaret reverts back to her first married name of Armstrong. Her second husband Alfred John Broman actually died in 1910 Breconshire. His daughter Bessie and her son are in Wales 1911.
So, bit of a carryon here not helped by the fibs told by both Mabel and her mother Margaret.
Annette