I agree with Star Witness. I have a female that is like this also, and females are considered to be very acrobatic. You can check this out if you are interested. Maybe you should take advantage of this, and teach your bird some tricks! This would be a good way to make of her talents.
Budgies are acrobatic and able to move much more quickly than humans. Their eye sight is special and much sharper than a human's. They have better reflexes than we do. They can see colors better than we can too: they can even see the ultraviolet spectrum!
Besides hanging upside down, my budgies will also do the splits in the top corners of their cage, and remain there for some time as if it were quite comfortable. They'd make great spies!
May does this sometimes - I call her my bat budgie. She'll stay in that position for ages. Midge doesn't tend to do it, but she does like to hang upside down while navigating the roof line of the triple roof cage.