I like this girl but is her friend interested in me?

To sum this up I'm interested in a girl I work with. I actually asked her out one day and it was obvious she was really shy and flustered by it. She said "i don't know" and pretty much took off in a hurry. After that she showed a little bit of interest but not enough for me to want to chase her around. But back to the topic this girl has a friend she is always hanging around with and I catch this girl staring at me quite often. And I don't mean just a stare I mean a pretty seductive look. Is this girl interested or is she scoping me out for her friend?