As many of you know, I'm an accepting and supportive GG. When I found out about my SOs crossdressing - because he'd finally reached a point of self-acceptance - I read just about everything I could get my hands on. My SO and I have talked, read the same books, and have continued dialogue on transgenderism and our understanding of it.
Since then my SO has always been totally honest about his level of crossdressing. It's the total 100% presentation - including forms, wigs, make-up, lingerie, hosiery, clothes, gowns.... etc etc - or nothing. If I had been spoon-fed little bits at a time I think I would've worried 'Where's this going to end?' It's something I often see on the FAB section of this forum too. GGs suspect their SOs involvement in crossdressing is much deeper than they've admitted... so GGs think their CDing SOs must have something to hide - trust starts to diminish because there are still secrets.
Of course, I do think you should take things slowly and at your GGs pace when you do finally come out to her, but that's different to adding one thing at a time - first make-up, then stockings, then wig, then forms - and waiting for her acceptance of each thing before moving on.
What's wrong with saying "I'm a crossdresser. Here are some books I'd like you to read. You can get support, understanding, help whatever at whatever website. And you can ask me anything you like about any aspect of my crossdressing at any time."
No more 'baby-steps' please! Just honest open dialogue.