"how to deal with inmature & unpleasant co-workers"?

I work in the medical field & customer service is priority at my job. I work with 2 others in my area - these 2 are in their mid-20's & have no ambition to go above what they are expected to do. When we don't have a heavy patient load, they spend a majority of their time on the internet, bring books, magazines to work, & have even painted their nails at their desk. Each of us is to have an even amount of providers that we manage schedules for, however, for over the last year, I have managed 6 provider's schedules, and 5 outreach provider's schedules while the 2 of them have managed only 2 providers between the 2 of them. Recently, one of our providers noticed that I was doing a majority of the work, while the other 2 visited or spent most of their time putzing. We now have to rotate positions weekly & our manager stepped in to relieve me of some of the providers that I was managing. The other 2 co-workers have not talked to me since this happened, and even though I have made attempts to ask them work-related questions, they don't even acknowledge that I am talking to them or even turn to look at me. I often e-mail, call, or visit with our manager due to the fact of the providers that I do manage are outreach providers for very specific patient needs, and there are issues or situations that come up where I do need to have direction on what path to proceed with. I do also manage 3 insurance company referral systems as they come into our department, so I am in constant contact & communication with our managed care dept & these insurance reps. The other 2 co-workers seem to leave me out of any discussion with what is going on with their provider or if something has been changed with how we are scheduling for a specific provider. I feel as though they are very inmature & may be a little jealous of my work ethic & the rapport I have with management & the rest of the dept staff. Most times, I feel as though I am the office manager in our dept. No matter what I say to these 2 co-workers, there is always the 1 that finds an argument against it. This is the same one that I get the most resented feeling from. Often times, she will make the comment to me that "You're not my mother!" I have to walk on egg shells around her, to watch what I say to her & how I say everything to her, but yet, she will hover around my computer & jump down my back & question me on "What does that patient want now?!" "Why are you in that patient's record - I just scheduled him?" I am constantly on guard with her. I absolutely love, love , love my job & I know that I am very good at it. I have always been very easy to get along with, and have never had a problem like this in the past. I realize that there are always going to be these kind of people around, but it makes is soooo difficult at work. Just wondering what steps I can take that won't include an all-out shouting match or workplace brawl.