Your wife should bless a container of water with the recitation of manis [OM MANI PADME HUM mantras], visualizing Thousand-arm Chenrezig above the container. Nectar flows from the heart of Chenrezig into the container of water, thus blessing the water very powerfully. Visualize that the water becomes completely blessed by Chenrezig.
Visualize this after every mala of mani recitations and do at least three malas blessing the water each day—not less, more is better. With the visualization, she must strongly believe that Chenrezig is blessing the water with nectar that purifies the four things, negative karma, spirit harms, obstacles and disease (the tumor).
When the visualization is finished, concentrate for a while on the water , thinking, “Now it is nectar.” She should sip the water several times during the day, taking several sips each time.
Keep doing this every day. When the water is finished, refill the container with water and keep blessing it.
With much love and prayers...