When she cries like that is it always for about 8 minutes or does it sometimes last longer? If so, how much longer?
My guess based on what you've said is that she probably has a stomach ache from being gassy. If she starts doing it more often or for long periods of time then you will probably want to take her to see the doctor. Otherwise somethings that have worked with my kids are: burping them (maybe she didn't burp well and has one "stuck"), swaddling them and wrapping an extra warm receiving blanket fresh out of the dryer around their abdomen, walking and swaying while saying 'shhhhhhhhhhhhh', and the swing and/or bouncy seat sometimes help.
There are 2 books that my doctor recommended to me that you might want to try and pick up from the library for more ideas if you can. The first one I haven't read but have heard a lot of very good reviews about is "The Happiest Baby on the Block" and from what I've been told gives a lot of ideas on things to try to comfort your baby. The 2nd which I have read was recommended to me by my son's pediatric GI and is called "Colic Solved" by Dr. Vartabedian. It has some good advice on helping soothe your baby when she's fussy and also on how to talk to your pediatrician about what's going on.
BTW, you mentioned that your daughter is on soy formula. Did she have problems with regular milk based formulas? Just wondering because the GI told us that most babies who cannot tolerate milk-based formulas are also unable to tolerate soy. Both of my son's have had problems with both milk and soy based and have had to be on either Alimentum or Nutramigen formulas. That's probably NOT what's going on with her if she's only crying once a day for a few minutes at a time but if it starts happening in longer stretches, it's something to consider.
A.