There is a fine line between feeling protected, guarded, shielded, and feeling caged.
We all - and a sub in particular - want some security and thus, being protected, guarded, shielded from “that bad world out there” can be very freeing, giving room to breathe and to sort out whatever may be bothering her.
This feeling of being protected can then turn into feeling caged when she realizes that the bond with her protector grows too strong, isolating her from her social circle. Not because he would request it but because she realizes she loses interest in them, he becomes the center of her attention and it is hard to escape that longing for him.
It is crucial to the health of the relationship to find the perfect balance between the two. Sometimes, being caged can be just what she wants but there may come a time where she would want to get her wings back and fly. Still being his but at the same time being herself, a human being with the need to reach out to more than just one man, no matter what she may think of this one man.
So allow yourself to feel shielded in your cage when the time is right for that - but don’t cut your wings, you will need them at some point in your future.