Why do some females grow taller even as late as 38-40? would that be minimal growth like few cms or what would cause significant increase like 3 inchs

They do not!: They may be wearing very high heeled shoes. Human females stop their height growth at about 16 yrs or about 2 yrs after onset of menses. Rare cases of growth hormone secreting tumors occur but there would be other signs of dysfunctional growth - I.e. gnarly fingers, enlarged eyebrow bones, etc. Think of Boris Karloff's portrayal of Frankenstein's monster!