It could just be because Lolli is a bit older that it's taking her awhile. Just keep practicing with her. She'll get it soon enough.
Just make sure she likes the treats you are giving her. You could try getting her more excited about the treat first. I just give them to Jasper and Riley randomly so they get more excited about them during practice. If she isn't too terribly excited about them try different treats. There's bound to be one that she loves. Riley is still really weird about treats. She doesn't like them too much. So, I give her baked chicken a lot. She really seems to like Pupperoni and Bully Sticks (although Bully Sticks take forever to chew).
Anywho, just keep up what your doing. Sounds like your doing fine. Just remember to put the treat over her nose and push the treat back (going over her head).
(On another note... I really recommend getting some Bully Stick. All four of my animals go nuts for them. Even the cats. In fact, my fiance tried them once (he can be a bit of a weird one.
) and he said they taste like really chewy beef jerky.)