How should I approach acclimating new kitten to us standing/walking?

My girlfriend and I adopted a kitten from a shelter one month ago, and she is now 5 months old. The shelter didn’t know her backround, just that she was a surrender.

At first she was extremely timid, and would hide in our closet, climbing up the hanging clothes to get to hvac ducts which she would sleep on top of. We followed Socialization Saves Lives’ socialization procedure as far as sitting with her, getting her to stand on us, eating out of our hands, but we let her stay in our room and attached bathroom and set up the closet as her safe space, and built in a climbing tower so she could get to her ducts easily. She will sleep in our bed now (I woke up this morning to her purring on my lap!) and approaches us to play and get treats- but only if we are lying down or sitting! If one of us gets up, or even moves like we might, she hops down under the bed and waits until we settle before hopping back up and going right back to playing. We are still working on petting, and she will eat from one hand while the other gently brushes the tips of her hair, and she does reach out to pull my hand down to play with (I don’t play back, but have let her hold my hand to her belly).

I know a lot of people recommend blocking off access to hiding places, but I want her to stay feeling secure and confident. We have been leaving the doors a little open to the rest of our apartment, and she does carefully explore now, but hates to see us standing or walking. She is very smart, and we do notice a pattern of he getting scared, going to a hiding place, then trying to scary thing again, so I wondered if anyone has maybe adapting the Socialization Saves Lives method to standing and walking? Something step-by-step to get her comfortable without forcing her to have no options to hide?