Was everything a Joke?

I found out recently that my gf for almost two years had a special someone back in the time when we were about to get into a relationship. I find it a total BS. When i told her I love her she immediately responded that she loves me too, then why the hell does she like someone else at the same time? God damn it I know Like is different from Love but for the love of God I swear she has cheating tendencies from what I knew about her, because if you can Love someone and Like somebody else at the same time, you're one hell of a person. I find it totally unfair that I regarded her as the only "special someone" during that time. Was she bullshiting me all this time? Maybe. Or it's also possible that she eventually just learned to love me as time went by. But it could be argued that she may have been "half-hearted" all this time evident by the quick decisions she made back then to break up whenever she's pissed. Bottomline from all of these, I learned that she can love someone and like someone else at the same time. WTF.  Enough said.