Funny that I should randomly stumble across this journal entry...I just finished reading Agatha Christie's Nemesis last night (a later Miss Marple book) and there seems to be at least strong hints towards lesbianism...the general gist of the novel is that a girl is killed by an older woman when the girl decides she wants 'normal' love-- to marry a man and have children. There are some mentions that the older woman 'loved the girl like a daughter' etc...but they're brief. Also there is an overt mention of 'crushes' that girls have on other 'attractive' girls or even on their female teachers that they eventually grow out of. I was surprised to find this in an Agatha Christie novel, having already read many of them. There was a couple comprised of two elderly spinsters in this novel as well, but they were revealed to have been hired bodyguards for Miss Marple. Anyway, if you are interested in looking for lesbian references, check out Nemesis.
spoilers below