Only if you want her to be.....
I'm fairly familiar with the manga and the anime and I've never seen her "hit" on Kagami so much as just annoy and tease her. Konata's obviously very fond of Kagami for putting up with her --- but anything more physical is never implied. Basically the fevered minds of yuri-fans is the only source for the idea. I can't say she *isn't* but then I can't say she *is* .... personally my speculation is that she's a
potential bisexual but we'll probably never get any confirmation within the storyline.
... not that it ever stopped any fan-fiction writers of course (ref: Kagami's brain bleaching experience at the anime convention in regard to her favorite manga characters)