I don't have any experience dating or having a mutual loving relationship, but I do know what it's like to be absolutely in love with your best friend for years only to have it be fully unrequited. You have to ask yourself if you will be able to remain friends with her after she is married without feeling your soul being crushed every time you think of or see her. Or worse, see her with her husband. My guess is that it will be difficult if not impossible. I'm also guessing that a major factor in your remaining friends with her for six years and likely devoting a lot of your time and energy to making her happy as well as presumably keeping yourself from entering in a serious relationship with someone else has been hinged on the hope that the two of you would eventually become something more than just friends. With that possibility no longer there, it's going to be different. It also sounds like you feel she lied to you, and indeed she did. That's got to breed some resentment.

Personally, if the friend I'm in love with told me he was getting married, a black hole would open in my heart and I would not be able to remain friends with him. That's pretty selfish, but I'm in love with him and have been in love with him for quite some time. I want to be more than friends and if that door of opportunity were sealed for good, it would be too painful and I'd walk away.

You can't make yourself fall out of love with some one. And after 6 years of platonic devotion, hoping, wishing and waiting, I don't think you'll be happy standing up there next to her as she pledges herself to someone else.

But, if you can look past all of that and can be truly content with just being friends, then go for it. It may actually work for you. You're hurting now, but some soul searching and deep contemplation may change your mind. But if you cannot, don't feel bad about it. It's obvious that she was never just a passing fancy for you. You've been yearning to have a meaningful romantic relationship with her for more than half a decade. It's not something a person can just shake off.

Ultimately it's up to you and what you're able and willing to do; both for her, but also (and much more importantly at this point), for yourself. Keep us updated and great luck.