I appreciate the hover-hint -ake (add agreement). It helps test me on adding the correct class/prefix :)
Why 'wake', but not 'lake'?
Because the noun before it, mzazi is an animate m-wa noun. Lake is used with ji-ma nouns in singular (if inanimate)
There's a table showing all the forms here.
https://en.wiktionary.org/wiki/ake#Swahili
Hivyo ni bibi wangu