Should I message this girl?

[Charlie]

Basically, there is this girl that really like from my church. I usually see her once or twice a week and we talk a bit - not lots though. I have never chatted to her on Facebook before however I really want to, to be honest. She liked my latest status update.. Would it be weird for me to randomly message her and, if not, what should I say? I'm not the best at starting conversations. Should I only msg her when she is online? If it was you, what exactly would you say?
Thankyou in advance

Extra information:
She wasn't at church yesterday so I'm guessing she is on holiday.
I think she likes me a bit because she looks at me differently to other girls, we both have the same favourite animal, she knows I love guitar and she plays flute, I'm a year older and I wouldn't call myself popular at school, I am, I think, a bit more at church though. I don't have her number atm , how could I get that because is it weird to ask her this late?
Thanks for reading my essay! haha

[Ghosts]

An essay consists of an opening paragraph, a minimum of three supporting paragraphs and a concluding paragraph, thus this isn't an essay.

[xoxo-gossip-girl]

well idk if you guys see each other at church i think it'd be better if you talked in person. from my own experience, i know that if you start talking a lot online but rarely in person it just makes it really awkward

but if you're gonna message her, wait until she's online, and talk to her about something you have in common (ex. church, music, etc). questions are always a good icebreaker in a conversation btw

good luck!

[isweetk1234]

Aww when she's online just say Hey, whats up. It won't be weird

[Anastasia]

(This is from a girls perspective if you don't mind)
So you could say some thing like, "Hey, what's up? I didn't see you at church yesterday, are you sick or something? :-)" and just talk to her like you would talk to your friend. You can tell if a girl likes you if she plays with her hair when she talks to you or plays with her clothes, and smiles, blushes maybe, even if she's mean to you she's trying to act cool so you don't know she likes you. Hope this helps! Good luck! ;-)