I would look at how you're feeling in therapy and how it may be "overloading" you? That's not a bad thing, quite good and necessary I think (was for me) but painful to go through. I would tell your therapist about your reaction, discuss it with her, and maybe she can modify the guided imagry or get your direct input so it's not so intense? Or, maybe you can make a tape for yourself, kind of copy what she says/is doing? You might have picked up a key with your enjoying her voice. Your mother's or someone's in your past voice you "longed" for might hold a key?

I know whenever I did anything intense in therapy there was always a reaction afterwards, especially before I learned to catch it during therapy and discuss it on the spot. I'd carry stuff away with me to where I was "safe" to fall apart and look at what was scary, etc. It was only when my relationship with my T evolved into a "partnership" and we discussed everything in the session that happened in the session that things got less "messy" outside the session.