What is it that you mean precisely by the phrase "earth love"? There is certainly a very real and genuine friendship between these two characters. It is at Lowood that we see Jane as a character finally able to make friends of her own age and also to learn significant lessons about life from them. It is important to remember that in this novel, the majority of the significant characters in Jane's life represent one of two extremes that influence Jane as she herself wavers between the extreme of unkindled passion and sensibility (as displayed in the character of Mrs. Rochester, and, to a certain extent, Rochester) and then on the other side sense and reason without any emotion (which we can see displayed by Helen Burns and St. John). Helen therefore does have a moderating impact on Jane's emotions, and therefore they have a very close link. Note how intimate the friendship is presented as being in the following quote:
Again I questioned, but this time only in thought. "Where is that region? Does it exist?" And I clasped my arms closer round Helen; she seemed dearer to me than ever; I felt as if I could not let her go; I lay with my face hidden on her neck.
However, Jane constantly questions Helen's beliefs and statements about life and in particular her passive stance towards trouble and misfortune, and this can be seen in the way that Jane questions Helen's faith that they will meet again in heaven.