Please check her INR ratio which is indicative of the deviation in Bleeding and clotting time. Apart from this, local factors in the mouth such as tartar and severe plaque accumulation leading to Periodontitis can cause mobility of the teeth. If she grinds her teeth in the night, the gum around the mobile teeth can bleed and pool up in the mouth at night.
Next Steps
Please send a dentist and have them take a full mouth X-ray and thoroughly evaluate gum health. Also with Physician if INT blood test is warranted