Should i feel guilty for having feelings for my good friend?

I'm a girl in my early twenties. I have a friend (also a girl) that I met about two years ago. We became very close because we were both dealing with similar life issues at the time - relationship issues, health etc. We really bonded and even though we don't live near each other we talk all the time. I guess if I think about it I've had feelings for her from the beginning, but the closer we get emotionally the more those feelings have developed. I always knew I was bisexual, but I've never actually had any experiences with another girl and I've never felt so strongly about one. I know she loves me (we say tell each other that) and I know she cares about me deeply too, but I don't know if she has any romantic or sexual feelings towards me. Sometimes she will say things that make me wonder a bit, but I know girls say these things to each other that don't necessarily mean anything beyond close friendship. It's gotten to the point now where I have a lot of guilt and feel like I'm not being honest with her. When I think about her I fantasize about having sex with her and how incredible it would feel to be with her. My mind is going crazy and because she's my best friend, I don't even feel like I have anyone else to talk to about this. I feel really guilty and I don't know what to do with my feelings. I value her friendship more than anything else and I'd never want to destroy what we have; at the same time I feel like I'm being dishonest and what if there's a chance she feels the same way? So confused.