I think it is up to you to tell us what the Victorian Flower Language is, as you are the one who has stated this is the language Snape is using. Do you have a link to an essay or anything? I have never heard it postulated that Snape was using the Victorian Flower Language when he first spoke to Harry and, while interesting, the onus is on you to provide the source of this theory.
Since you have not in any way proven the existence of the Victorian Flower Language, I will err on the side of taking J.K. Rowling's words at face value:
‘For your information, Potter, asphodel and wormwood make a sleeping potion so powerful it is known as the Draught of Living Death. A bezoar is a stone taken from the stomach of a goat and it will save you from most poisons. As for monkshood and wolfsbane, they are the same plant, which also goes by the name of aconite.’
Philosopher's Stone - page 103 - Bloomsbury - chapter eight, The Potions Master
Here's what I think is ultimately most important: Dumbledore said to Snape in Deathly Hallows, which is revealed in Snape's memories, "I shall promise never to reveal the best of you, Severus." I'm paraphrasing. Anyhow, Dumbledore's telling us that he will never reveal Snape's love for Lily because it was so deeply personal and painful to Snape, even though it was love. This calls into question whether, in any language, Snape would openly reference his love for Lily to anyone, much less Harry Potter, the son of James Potter, Snape's hated enemy and the boy Lily chose over Snape.
I don't agree with your theory. Even a cursory review of Snape's characterization just doesn't allow for that kind of sentimentality. I definitely err on the side of J.K. Rowling rather than Edith Wharton when it comes to Harry Potter (and believe me, I love the Edwardian/Victorian eras!)