Search Results: keep it platonic

So there's this girl that I have known for about 6 year, and I have had a crush on her for the past five. At first I didn't ask her out because neither of seemed too be to big into dating in middle school/high and four years ago she turned into a family friend, so I thought it would be best for both of us if I played it cool and kept her at a distance. So for a long time we didn't see each other much, but when we did we always really hit it off.
But than 4 months ago we had this 2 hour heart to heart, and I kinda fell for her (again). One thing led to another and a few weeks later we were seeing each other 5 times a week. I talked to my mentor and my family about it and they all said I should go for it, and I decided I was going to ask her out right before winter break (so that I would be able to give her space if she wanted it).
But than everything went south. We now share this clique of six other girls and me, and one night we were talking and one of them thanked me for being such a big brother to her. My crush than thanked me too and started talking about how weird it was that I was like a brother to her even though I was so different from her real brother.
I am not quite sure how I should be reacting to this situation. But I know 6 things for sure
1. She doesn't owe me anything
2. She has no idea I like her and has probably never considered us being together
2. This hurts
3. I don't want to hurt her or the people around me
4. She is better at and has more experience with opposite sex platonic relationships.
5. She and her friends trust and idolize me
6. I feel like telling her and not telling her how I feel is betraying that trust and destroying my relationships
7. I am probably overthinking this...
Advice?