Thanks. You are most likely feeling a lymph node or salivary gland. A lymph node may be enlarged due to antigenic stimulation/inflammation/infection drainage or cancer (less likely in a cat so young). A salivary gland may be enlarge due to infection, cystic lesion in the gland or cancer (again, less likely in a young cat). Drainage from an infection in the mouth or facial area usually causes that lymph node to enlarge. You can often get tooth root abscesses without any outward signs in the mouth or pain. I have seen them before with very clean mouths. It doesn't sound like an emergency, but I woud get her in to be seen on Monday by your vet. They may want to aspirate the mass to get a diagnosis, but she will most likely go on some antibiotics. Many of these enlargements decrease with antibiotic therapy. Please let me know if you have any other questions. Hope this helps.