Your cage size is def large enough, two by two may be a little to small for her at that length and girth. I wouldn't put a larger one in there to be honest,since she doesn't use it as often as when she was younger I would think removing it and not putting in another would not effect her behavior. I have seen removing cage furniture halt some snakes feeding (ball pythons), I have never noted this with my retics or burms, I use hides for all my Boids when they are smaller and when they get "too" large I simply remove it from their enclosure and stick with a simple set up, newsprint and water bowl, my snakes are eating and have reproduced in this type of environment. I must note they do sometimes hide under the newspaper, so they still want to hide, just providing a hide large enough in a 6 to 8 foot enclosure becomes next to impossible for the reasons you stated, so the snake will hide even without a hide box, unless your substrate somehow prevents them from doing so.
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Frank Roberts
R&R Herpetological

Roberts'Realm of Reptile Research