I take it that this someone is your best friend, but now you've developed a love interest, and this person has not, and has now found a love interest of his/her own.

You can still be friends sweetie, but I think I would back off a bit, since it's hurting you so much. Who would want to hang around someone all the time when their feelings aren't being reciprocated?? That would be TOO painful for anyone!! Why not just see this person every now and then instead of all the time like you are now? Don't torture youself. Perhaps in time this person will realize how much they miss you, and will also realize they have feelings for you too! Give it some time. It may OR may not happen. You just have to wait.

In the meantime, don't torture youself. Stay clear as much as you can and find other friends to spend time with. I'm sure you have a bunch of other friends. I wish you the very best. Will you please keep us informed? I'd appreciate it. God bless & take care. Hugs, Lee