I always just put a drop or two of rescue remedy (or any bach flower essence) onto my nipple, or onto a finger tip that I then let my babe suck on. You could use a paci or bottle too I suppose.
The only concern I can see is that the carrier liquid is generally alcohol... you can dilute it in water and then use the water, or I believe there may be a few "alcohol free" versions (but those go bad sooner, and need to be kept cold). I'm not concerned about one or two drops every now and then, but if you are then perhaps the water dilution option would feel better.
I feel your pain though... colic is horrible! Since you say it's every once in a while, have you tried gripe water? Or checked your diet to see if she is reacting to a specific food you've eaten? My dd1 would have horrible gas pain about 8 hours after I ate peanut butter. I stopped eating PB&Js and the gas pains stopped. It took a little detective work, but not a lot... I think I kept a food/fuss journal for about a week? Just jotting down what I ate, when I ate it, and when dd1 was fussy.
Good luck!