Hi Annette
Your story does echo mine, as well. Only I gave up the BFing completely at about 3 weeks because I couldn't handle being vomited on 7 times a day. On formula it just meant that DH and I shared the vomit!! Poops were a nightmare, absolute nightmare. When you describe them as frothy and whippy, to me it sends up a red flag as that is NOT normal. My advice, as yuck as it is, is to start taking pictures. It was one of the only ways that I got a good diagnosis from the paed - and he was thankful for the photos and said he wished every parent did that, as descriptions can't do what a photo can!
My LO also had "suspected" reflux, although when medicated it didn't really go away - the one thing they gave him that did help him stop puking actually made his poops worse, and it was because his puking was a way of getting the milk OUT of him, but by us forcing it to stay IN, he had nightmare poops.
What formula are you on? Is it Nutramigen or Neocate? Is your GP sending you to a paed/gastro doc for further discussions or clinical diagnosis or support? I would request it, unless your GP is very confident and comfortable with these kinds of problems. I know most GPs aren't mainly because they are not specialists. Our hospital paed didn't really "do" anything but he was a wealth of information that I couldn't have learned from my GP.
I am of two minds with the BFing. I had always read on BW that if you were BFing an MPI baby, you needed to eliminate all dairy from your own diet, however, I have a friend who has an MPI baby and she was okay BFing him, as long as she kept her dairy intake very low. May be something you want to think about. She got her LO onto Nutramigen and kept only her morning and night BF and cut most dairy out of her diet and her LO was okay while she weaned those last two feeds. But, there are BW mothers here who have breastfed MPI babies who can't have a sniff of cheese or their LO will react - I think it depends on a lot of different factors. As I didn't BF I don't know how you would decide how much dairy you needed to cut out. BUT if you have her on the hydrolysed formula and she is still acting as above, then I would think you would need to either eliminate dairy from your own diet or stop BFing if you find that too difficult (I know for me I am very dairy dependent, there is no way I could survive dairy free, I would not be able to consume enough calories to keep milk supply up!!)
With how long it takes to get the milk out of her system -- you should notice a fair improvement within a few days to a week, but again if you are continuing to BF and consume dairy yourself, then you may not notice large improvements. And then, once she is completely dairy free, the "rule of thumb" that our paed told me to go by is half as long as she was on the dairy for. So, in our case DS was on some form of dairy until he was 5 months, so he told us it could take up to 2.5 months to see a full recovery. And, sure enough, I would say it was about 7 months before things were totally cleared up.
You asked if she could develop an allergy by keeping her dairy free, and the answer is no. Absolutely not. Quite often humans (adults and babies!) do get a temporary lactose intolerance from prolonged periods without consuming milk, but this isn't any concern, really, as it's not a true lactose intolerance, it's just the body needing to remember how to break down the lactose, rather than the body not possessing the capabilities of doing so. And, on the flip side, if she is milk allergic/intolerant then continuing to give her milk/dairy is not going to help her learn how to tolerate it or break down her allergy, you can actually cause her more problems by continuing when she should be off of it.
As for the adding fruit puree to the milk...I'm not 100% sure about that. I would be more inclined to express some BM and mix it with the formula than add the fruit. My son went from milk formula onto soy formula (turned out to be soy allergic as well) and so when we switched to the Nutramigen it took about a full month of mixing the soy and Nutramigen to get him to drink the Nutramigen. I know some moms have done it with EBM as well, but if you are not used to pumping or don't have the supply I'm not sure if you would be able to? Sorry, my BFing knowledge is limited to what I read here on BW. We started with mixing the soy and Nutramigen by just adding a couple of ounces of the nasty Nutramigen, and every 3 or 4 days one ounce less of soy and one extra ounce of Nutramigen.
Not sure what else to add.....had to go check on DS so I sort of lost my train of thought. Let me know if you have any more questions, there are lots of us here who have been through this!!!