Well I'm a female (married, straight) who says 'I love you' to at least one of my female friends (also straight) and means it - she is like family to me. So yes, I can understand that it's possible to 'love' friends, it's not like romantic love, but it's special IMO.

The thing with the boyfriend - I can remember feeling jealous and 'put out' when a good friend (many years ago when we were teens) fell in love with a great guy and got serious. In my case it was a deep seated insecurity that I would never find the love and companionship that those two so obviously had, I was jealous/envious.

I can't help but think that this is all tied in with your own anxieties over your relationship break up and likely fear of rejection, except it is being focussed on this instense friendship.