I thought this girl liked me? Added me but hasn't seen my message yet?

[Patrick]

I met this girl saturday who was a senior and my mom's friend's sister (I'm a junior). She seemed cool but quiet. We made eye contact frequently while laughing, she chuckled at what I said during group conversation, etc. The next morning she added me in Facebook so I accepted a couple hours later. Later that day, I messaged her and she still hasn't seen it to this minute. I realized she is briefly active on Facebook for messages but its hard to believe that she still hasnt seen it after two days. Is she not expecting the message? How do I let her know that I sent her a message? (Because I hate waiting) or should I wait a bit longer? I also don't want to wait very long because I don't want her to forget me and I don't want to lose my chance at a possible relationship.

[Mohannad]

I advice you dont rely on fb in your relation
try to talk to her or mybe your mother can help you