I've known this girl for a while now and I really like her so I asked her one day on Facebook if she felt the same way but I got no reply, can anyone give advice?

Everyone expresses how they feel differently, but it sounds like she's not interested. You should ask her face to face, she will respect you more for that and you will be able to read her face :)

No reply can mean a lot of things. Either she's very shy and couldn't answer or she's not into you.

The only way you can really find out is to ask her in person. Body language is the best way.