ILR and dependent child

I am a UK citizen. My spouse and step-daughter arrived in the UK in late 2016 and have now gained further leave to remain here in the UK.

My wife is considering a return to her own country to follow her career in international development which will mean she would not be granted ILR. My step-daughter was 17 when she arrived and has FLR until late summer 2021, after which she will need to apply for ILR (she will have been here 5 years at that stage as a dependent child).

Am I correct in assuming that because my step-daughter is here as the dependent child of my wife, unless my wife gets ILR, there is no way that my step-daughter can get ILR, even though she has been here 5 years by that time and will be 22 years old?

since there is no absence threshold then if she can then maintain her residence even with absences in UK until ILR.