My girlfriend of 10 years says she loves and still Fancy's me but not in a ual way.?

I'd lived with my present girlfriend for over 10years. As partners we had 3 successful business's, enjoyed each others company and very seldom argued about work or personal issues. We also had a lot of trust and loyalty for each other. Admittedly we didn't take much special time out but we both seemed happy with that. Now then, had never really been a big thing with my girlfriend and in the early days I put this down to her grieving the loss of her brother to whom she was very close. On talking with my girlfriend some time after, she admitted that really wasn't and hadn't been a big thing with her even in past relationships. With everything else been almost perfect I respected this and would happen maybe half a dozen times a year if that, sometimes myself making the advancements sometimes my girlfriend. Last year we invited a new friend into our lives both on a business and personal level. He was a great character and would do anything for either of us and ended up been very close. Then the blow happened. He had been staying over for a few nights and me having trust in both him and my partner left them talking one night and retired to bed. The same night I was suddenly wakened by muffled noises that made my heart sink. I walked into the living room, to see what I really didn't want to see, both of them oblivious to me standing there. I slammed the door to and broke down. Missing out all the detail on arguments etc, I basically threw her out and told her to go and live with her new lover. Days later, my girlfriend admitted that our trusted friend had not made any ual advances, and that it was his presence that wildly turned her on, something she'd never sensed with anyone before. She concluded her confesion by saying she lost total control and just had to have him no matter what. On returning to her new nest she admits this strong magnetic attraction still happens whenever he's around, but thats all. In her words, not mine, he is the lover and has little other qualities, whilst I am her soulmate, her rock, and the person she loves and still fancys but not ually. Can anyone throw some light on this please?. I'm totally stumped to whats happened. Maybe an outsider can draw the conclusion? At the moment we still continue to run our business's but on a half hearted basis.