I tried to find them in 1901 but the only Matilda Mylchreest family didn't look right, and she was recorded as b.England. (Later - this family was still in England in the 1911 census.)

Annie's birth in 1898 appears in the Lancs Birth Indexes, in Toxteth Park, Liverpool, Ref.TP/402/65, but I didn't find her in 1901 either.

Re. the "14 years" married in Matilda's 1911 census record, there is this entry in ManxBMD:
Year Surname Name Parish/Town Where Married Page Entry Register:
1897, Mylchreest, Peter, Marown, Marown, 38, COE
- but no matching Matilda found, or Alice.

Ethel's birth?
1904, Mylchreest, Ethel Isabel, German, [Vol] A, [page no] 469.

I had a look at the scan of the 1911 census. - Matilda had terrible writing, and her name was written "Malil da" or "Malil ila". There is no cross stroke on the "t". Spoke both English and Manx.
And she signs the form "Mrs Peter Mylchreest" - yay!

The death in ManxBMD is pretty close in age to the one she wrote in 1911:
1915, Mylchreest, Matilda Alice, 43, Onchan, [Vol]A, [Page]1715.

It is possible that in 1901 she was recorded as Alice Mylchreest, serv., Married, aged 30, Housemaid domestic, b.Marown, in the household of Margaret Allyn, 61, (with Kelly daughters) a Boarding House Keeper, 25 Lock? Promenade, Douglas St Barnabas, Onchan.
Household Schedule Number:13
Piece:5303
Folio:127
Page Number:3

Annie not with her.

Sue