Managed to access the microfilm of the WCC Karori Burial Register:
#7044 GARDNER Lena Gertrude, buried 27sep1905, aged 24 years; from the Hospital; Rev Dawson officiating; E Morris jnr, Undertaker; burial plot - 46F.P2
#6306 GARDNER George Potter, buried 4aug1904, aged 73yrs; of 13 Webb St; Rev Dawson officiating; E Morris jnr undertaker; burial plot - 75E.P
#1710 COOK Annie, buried 18feb1896, aged 40yrs; of Webb St; Rev W Hall officiating; E J Morris, undertaker; burial plot 75E.P
Can only consider that the omission of Lena from the online listing was an oversight. It will be interesting to see what info WCC Cemeteries provides.