Start by searching around the house for paperwork, also check emails and docs on computers. She will probably have saved passwords and pins somewhere either in a notebook or on the computer. The invested money must have come from somewhere and will probably have passed to the the investment bank from her main bank or building society so the transfers should show up on bank statements. I hope this helps. Pretty soon also she should be getting end of year statements either through the post or by email and that also should give you some leads. Does she have an accountant? If she has invested that much money, she will probably have had to declare if for tax purposes and may have some tax paperwork still.