I brought my cob a himalayan naf salt lick last wed's, thing it's 2kg weight, she's prob about 1/3 of the way through it already. She's on box rest and only coming out 1/2hour am and pm to graze.
She is either lacking something and is making up for it, or she is bored, I would go with the bored idea.
My horse only occasionally licks his, the horse next door is obsessed with his one!
I would be inclined to remove it intermittently, just in case. Try putting carrots etc in her hay net, putting a radio on and maybe getting one of those balls you put feed in, although my horse gets frustrated at these and stamps on them!
I thought about taking it out but she'll probably just lick it more when i put it back in. Unfortunately she's recovering from laminitis so she's not allowed carrots but she has got her hay in very small hole nets.
It's taken my boy about 5 months to get through his salt lick - I hung it up in the stable for him and he wouldn't go anywhere near it so ended up putting in his feed bowl and he still won't lick it but it must leach into his food and takes forever to go!
Chancer was like this initially but after a few weeks he stopped eating so much, think the novality wore off and now licks last about a month or so when he is in during the winter.
Make sure she has plenty of water and ad lib hay if possible so you know she is not licking it as she has nothing else to "feed" on.
My 15.2hh TB kept breaking the panels through to his friends stable to have a lick on his Himalayen salt lick so i brought him his own today, will see how long it last!!
we had one of those large bucket sized ones in our feild and when our little 12hh pony got out of his fenced off area it got eaten in the space of about 2 hours followed by the desruction of the plastic box and then the systematic rolling on all the bits of box just to make sure there wasnt a bit of his body that didnt have the sticky residue on it!!