lovebird always on top of cage?

[littlestever]

so its been about 2 months now since i have been with my lovebird (luna) and she seems to be very friendly with me at times. i have no problem getting her out the cage and hand feeding her or even getting her to come on my finger or shoulder sometimes. but then there are times where she dosnt always go on my finger and she just flies around the room chirping. more often she seems to always fly up on top of the cage and she just sites there chirping on and off. when i try to get her she runs to the back corner of the cage as if she just does not want to be touched. i feel like i have to force myself to get her to go on my finger to try and calm her down. is she just scared ? should i just leave her alone and let her continue to chirp in that corner?

[littlestever]

http://imageshack.us/photo/my-images/812/img2959lg.jpg/ here is a picture of my bird on top of the cage