Couple things for you to try. Mylicon drops help with gas HOWEVER they are constipating (They slow your gut down, which blocks you up). So if she's constipated not a good idea. Try full strength prune juice or apple juice then follow with a nice warm bath with baking soda. I usually add 1/4 box per bath. Just be prepared for her to poop in the bathtub when you do that (It helps to relax their spincter muscles). I also recommend a warm towel or pillow case on her tummy. The heat works to help stimulate her tummy nerves and move the gas and poop along (I usually iron a pillowcase or hand towel just until warm, but not hot) Milk of Magnesium works well too. And they do make a baby suppository, but usually you want to clear her from the top of her gut down. Suppositories and enemas are LAST resorts. I've been dealing with a constipated child for 8 years, and we still have to work on it. Once you get this straightened out, I would recommend that you start her on some daily baby yogurt,like yo baby. This will help with the good flora in her tummy and hopefully keep it from becoming a problem again.
If none of the above works, or any of the following occur:
--Continued screaming
--abodomen is swollen
--she starts vomiting
--her poops look different
--or she develops a fever,
you need to call your pedi IMMEDIATELY. DO NOT WAIT. PM me if you have any questions. I'm an old pedi nurse pre SAHM days.