They like tubes as they are small and inclosed and they feel safest in there. However it is not good for them to be inthe tubes all the time, it can become stuffy, damp, and smelly in there, especially if they pee in there too.
Whats generally reccomended is that you remove the tubes for a while (a week or 2) and encourage her to establish a nest eslewhere in the cage, perhaps in a box, or a hamster house. Removing the tubes for a while also helps with taming, as they cannot hide up the tubes where they know you cant get to them!
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