Would it be weird to message a girl now?

[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

[Brenda Fleming]

Just message her right now with a simple 'Hello'. Don't make things complicated about this situation.

[kaylee]

Just say hey.

[Anna]

you should!! say hi and then maybe a cute pic of ur guy's fav animal reminding her of ur common interests could make it seem more.... Interesting XD but im serious

[Sarah]

Just say hey or ask her why she wasnt at church so that gives you something to talk about and it wouldnt seem as strange. But if you think shes on holiday you usually wouldnt be going on fb that much so dont get offended if she doesnt text you back straight away