If you are not sexually attracted to her, you have your answer. There is no reason for you to have sex with someone unless you think you will really enjoy it and get a lot of pleasure and satisfaction (unless you are just interested in having kids, and that is not the case here).
There are other reasons to tread very carefully here. Sex DOES change friendships. Most the time, it disrupts them and often ruins them. It is pretty likely that things will get really strange and awkward after sex and you will not know how to relate to each other like you once did. Are you willing to risk this? Why? How important is it to you that you keep this friendship for life?
To be honest it sounds like she might be having certain emotional problems or insecurities, or extreme loneliness, or something else, that is not clear. Most people who are close friends do not talk to each other about how great it would be to have sex. If she is emotionally fragile now for some reason, that is another reason to keep it at the friendship level. And what is wrong with that? True friendship is one of the closest forms of intimacy there is.