What comment does Charlotte Lucas make about Jane? Why?

Without more detail, the quote I've chosen is...

"It may perhaps be pleasant," replied Charlotte, "to be able to impose on the public in such a case; but it is sometimes a disadvantage to be so very guarded. If a woman conceals her affection with the same skill from the object of it, she may lose the opportunity of fixing him; and it will then be but poor consolation to believe the world equally in the dark. There is so much of gratitude or vanity in almost every attachment, that it is not safe to leave any to itself. We can all _begin_ freely--a slight preference is natural enough; but there are very few of us who have heart enough to be really in love without encouragement. In nine cases out of ten a women had better show _more_ affection than she feels. Bingley likes your sister undoubtedly; but he may never do more than like her, if she does not help him on."

She makes this comment in response to Elizabeth's revelation that Jane has her eye set on Mr. Bingley.