Hi Darlo-
The dead hear our prayers, so prayers for peace and comfort are always useful, just as Kardec says.
Retrievals may or may not be appropriate, dependeing on whether anyone's stuck in the borderland areas of astral. In the same way, if anyone is stuck on the survivor, that should be handled gently so that they can be released to go on.
I've never been very concerned about calling up the recently dead, as the peace of the spirit world is usually liberating. Putting the surviving person in trance, such as by hypnosis, and suggesting that she call for the others to communicate with her should be effective.
If there remain strong emotions, those will eventually need to be replaced by forgiveness or they will serve as "glue" to hook onto unpleasant karma.
My suggestion would be to seek out an experienced and Board certified past life therapist, so that she will have someone experienced with this type of work. A site that I'd suggest is
www.IARRT.org where you can find a referral to an experienced past life therapist.
I'm personally available in California, if that is appropriate. You can find data on me at
mbs-hypnoclinic.com among other places.
To my mind, the most important thing is to get rid of strong negative emotions, first through forgiveness, then by developing love, wisdom and a decision to be joyful.
good luck-
dave