OP,
My thoughts are with you today. Liberty is being remembered here. 
IMO, you AdefinitelyNBU to want loved ones to acknowledge her birthday.
Whilst I can totally understand hesitancy as to whether mentioning a child's anniversary/ birthday might be unwelcome or upset a bereaved parent, and erring on the side of not, your posts clearly state they have been there all along and are fully aware as to your wants and feelings about significant dates/ milestones.
Unless informed otherwise by you, why should that change after 5yrs, 6yrs, 7yrs...
(I agree: it's sad that some people interpret grief lasting any longer than some arbitrary period of time they judge appropriate as not having moved on/ not worked through feelings etc.).
As to forgetting the actual dates, it's hardly taxing to stick 2 reminders on a flipping phone or calendar, is it?
I have no personal experience of the utter devastation that the death of a child brings...heartbreaking even to imagine, but to experience it must be pain of the cruellest kind. 
But in case (God forbid) someone close to me were ever in a similar position, may I ask bereaved parent MNers here if lighting a candle and/ or making a small donation to one of the Stillbirth charities, (SANDS/ Tommy's/ ISA) in honour of the child's birthday, would be seen as an appropriate gesture from a close friend? Or too intrusive and OTT?