I think you can ref. my experience.
When I employ this yan yan, I directly tell her I am using a bun bun now. But she works very slow. I won't give her any warning (save gas). When your visa is ready, I will directly fly her.
Luckly, this yan yan work quickly. She can cook for dinner in 30 mins with 3 dishes... And she always ask me if she do something wrong, I should tell her and give her chance to improve. She worry that I will fly her like the ex-bun bun!
My yan yan tell me some agent tell them 做又36, 唔做又36, 教佢做慢d...........so that we will change for a new yan yan. Then the agent can earn more from the yan yan if we change them. My yan yan tell me don't trap by the agent!