you don't want to lose her, but you don't want to be needy

that is a contradiction, if you are worried about losing her, you are needy by default,
go out get other options, game other girls, talk to new girls, try to take them out, still continue trying to see and progress with this girl, but you have to emotionally re-gain control of yourself, you are being sucked in to having a oneitis
you have to change your mindset from,
I need this girl, can't fuck this up, have to do the right things to get her to like me
into,
she already likes me, I have this in the bag, if she does something lame I might move on, but right now this looks good
basically, you are already needy, the way you are on the inside will always shine through, you have to actually control yourself and actually realize you are being needy and stop it, be wanty, not needy, want her but know that you can move on at any time if it is not working out, she is just a girl, you don't need her, there are plenty more out there, I suggest you create other options for yourself fast to help you distance yourself from her emotionally, before you get too emotionally invested in her and turn her off
GOOD LUCK