Please calm down. They are far less likely to sting than are honey bees.

Unfortunately, many people have a natural fear of stinging insects that they have very little control over. Especially if she comes from a family where there is a pervasive culture of insect fear. I would encourage anyone with a debilitating fear, which she has, to see a therapist who specializes in treating phobias. In the short term, get a friend to go into the garden with you to see what is going on under those boards.

Martha

Are you certain it was a bumblebee? I've only had carpenter bees stalk me, and not to suggest you don't know the difference, but many people don't and generally assume.

You might ask someone to come into your yard and flip or move the boards on the ground. That will help identify where there are bumblebees, and help to encourage them to leave the area. Bee allergies are too serious a thing to be taken lightly; your life really can be on the line if you are stung and have a severe reaction and do not have appropriate treatment readily available. Fortunately, bumblebees I have encountered seem ready to leave a nesting site fairly quickly if disturbed.
Renais