OP, you got a simple decision: Move on and stay friends with her, or move on and cut contact.
This is based on one simple question you have to honestly search yourself for the answer for?: Can you honestly be her friend and move on at the same time?
No? Cut contact, meet new women.
Yes? Cool, hang out with her some times, meet new women.
If my experience is anything to go by she may try and ****-block you out of jealousy, because something misguided in her noggin leads her to believe she can 'keep you to herself' despite having clearly rejected any romantic prospects and settled for friendship. If this occurs don't let it bother you, it doesn't mean she wants to be with you at all, she merely feels you are her 'property' and enjoys the attentions (real or perceived) she may feel you provide, an ego boost etc.
Thankfully most women when they don't desire you that way are cool about it, so use that resource, that connection to meet her mates. Just be wary of those that may actually try and block your attempts at freely associating with other people in a romantic/sexual fashion.
This as well.(Original post by Forum User)
Whichever option you choose, don't do this again. If you like Girl C, make it obvious immediately instead of pretending you just want to be her friend for months and then being surprised that she just wants to be your friend.
That does not involve 'telling her that you like her'. Telling someone you like them is what people do in year 9 at Secondary School.
Sorry if that sounds harsh.
You're a grown man and should be able to own your feelings and intentions. If you like someone then flirt and be pro-active.
Friendship is fine... between friends.
How are you celebrating?