Your vet seems good and I would take her advice ... she probably has a lot of experience. The great thing is that whatever it is, you caught it early. I caught a lump quite early on my newfy gal's breast and she had surgery to remove the cancer within a few days. Total cure ... as of 1.5 years now.
I'm not a nurse but we give our dogs belly rubs ... oh, about 10 times a day! Great for picking up the lumps and bumps!