How To Text Message Someone On Facebook?

[John Dennis]

lets say i'm inside a building, i can't call out and i can't get internet while inside, but i can text someone. my sister doesn't have texting on her phone but is almost always online on facebook. i know i can set it up so someone can text me from facebook to my phone but that requires that i have to receive it in order to be able to send a message back but is there an app or a way i can message her from my phone to facebook because i won't be able to message her any other way and sometimes she has to pick me up something while i'm grocery shopping but it unable to get up with me, but what if i need to message her because i can't wait for her to message me first.

I'm using an Android if that helps.