Ok, I see a lot of mothers on here who are SO anti-binky... and I don't see why. Here's my take on it- if it makes her feel better and it soothes her, making her a happier and more secure child then what's the problem? Its a GOOD thing when a child finds a way to self soothe him/herself.
And I can assure you that from a dental stand point (I work in dentistry and have for 11 years) that there is NO damage being done by using a binky while a child has their baby teeth. So unless your 5 year old is using a binky you have nothing to worry about. The space that's there SHOULD be there, as spaces between young children's teeth are a good thing. It means there will be plenty of room for the new teeth to come in. The binky MAY open the space a tad more than if she didn't use one, BUT it will not affect how the new teeth come in when she's 5-6 yrs old. There are TOO many misconseptions about binkies ruining a child's teeth.
My son is 14 months old and he LOVES his binky. He doens't always have one in his mouth and there are times when he could care less if there's one around. Sometimes he even just carries one around, because he likes having it close. He is a happy, well-adjusted child who sometimes needs a little something to help him feel good. And I'm ok with that. I don't see the harm in it all. I think its important to let our children decide (when its appropriate of course) what they need.... and obviously your daughter has some sort of need for that right now.
Good luck with everything.... take care!