K.,
I won't repeat everything that's already been said. I'll just say that I agree with the moms that say wait for allergy, age, AAP, WHO and "it doesn't work for everyone" reasons.
At four months your young one still needs your comforting a lot. Since you work during the day, she gets her mama lovin' in when she can, at night :-) Also, keep in mind that no matter the age, breast milk digests in about 90mins. The reason bf'd babies eat more often when they're younger is because they're unfamiliar with the uncomfortable sensations caused by hunger. At 4mos your dd is dealing with those sensations in her tummy fairly well.
*Most* babies do wake less at night than every 3hrs. It might be the routine of it. Personally, I am anti-CIO. I would recommend instead "The No-Cry Sleep Solution" by Dr. Sears. Your library might even have it. Your local LLL chapter or API chapter might also have it. If those are not available, then you can find it on Amazon.com for less than $6 used.
Also, although a lot of babies seem to "sleep thru the night", very few of them stay that way. My Nursing Support group in Oregon joked that whenever you settle on a given thing as being the norm with your baby, go ahead and prepare for change. :-) That to say, your baby may not be sleeping exactly how you want her to right now; She may be nursing way more than you want her to; try to back up and think about how quickly this age will pass and she won't 'need' you near as much. They grow up so fast - why speed up the process?
Here are links so that you can find if there is a LLL group or API group in your area
http://www.attachmentparenting.org/group/webtx.shtml
http://www.llli.org//Web/Texas.html
Congratulations SuperMom on nursing successfully and working!
HTH
K., mama to
Catherine, 4y
Samuel, 14m