1) yes
2) no
3)Breast milk can take up to 2 weeks to be clear of food proteins.
4) You can be ok w/ soy (or anything else) for a few days and then start reacting.
I'd talk to your ped and if they don't seem understanding of a possible allergy or reflux, get another one. I love mine if you need one. Also, i'd call a pediatric allergiest. We go to Children's Memorial at the Glenview location. Dr. Kim is there on Weds. 1-800-kids-doc.
It sounds like an allergy. I'd start a log of when you feed her, what she gets, when she vomit, sleeps, screams, sleep etc. It'll be helpful.
My dd vomits nonstop 2 hours after cows milk. She also had an egg allergy (outgrown). We also did reflux meds for her 1st year. Had we known about the allergy sooner, maybe some of her symptoms would have been better (i supplimented my breast milk too). We found out at 10 months.
You can also try nutramigen (sp) in the meantime. Not sure if it's soy or cows milk though.
If she's cow's milk allergic, all the other animal milks will affect her. Also, any milk product would do the same. Some kids even react to trace amounts of dairy in bm. Like if I ate a product with casein or lactose in it. www.foodallergy.org has great info and can get you a complete list of foods to avoid (all the many names of milk for example). Also www.kidswithfoodallergies.org is an amazing resource of 8,000 parents of allergic kids. I'm on there everyday and it's saved our lives.
email if you need more info. good luck!