one of mine tilts her head a lot. I think they just find it easier to see the food object if looking out of one eye rather than 2. if you got that close up to someting and stared at it straight on it would be blurred and you'd go cross eyed probably. so I think it just helps the leo see it properly.
I have another leo who looks strsight on at the worm and them misses many times. I think he needs to adopt the head tilting method lol!!
hope this helps. I wouldn't say there was anything wrong with the eye, and even if there was I'm not sure there's a lot can be done for leos with bad eye sight. as long as she doesn't seem to be squinting or acting differently I suppose.