Girl I secretly like jokingly admits she loves me. Should I take it as a joke?

[appleguy123]

This girl I really like today said she loved me in in casual conversation. Here is the abridged story. This girl is one year younger than me and in my band class. We have been friends for awhile and we sit next to e/o. She has made some advances towards me (holds shoulder leans toward me...) but thats not really abnormal for her with other guys too.
Now it took place like this.
Me: Why don't you make a Facebook account?
Her: (jokingly) So you cannot be my friend on there
Me: (jokingly) I hate you.
Her: (quick response) I love you.
Everyone at lunch table is like Wow!
She never took it back but continued to act normal.
The question is should I take this as a joke or something more? If I ruin our friendship from misreading a sign I would be really upset.
So please help me out. This will be my first GF (Im shy) and I am 16 (really weird I know. So thanks for the help!
A few more details. This is my best friends sister (really weird) but I know he trusts me because all three people I have mentioned here believe in abstinence before marriage.
Also are there any tell-tale signs a girl likes you?

 

[n0rcal]

Be careful here, a lot of girls use this with their guy friends...I would wait and see what happens, for now definitely don't read into it. Good luck!

 

[GinnyD]

It sounds like a joke. Maybe after that she was so embarrassed she didn't know what to do but to act casual.

My best advice is to just bring it up and talk to her about it. Don't start wondering too much about it and don't look into it so much.