reasons for blister include -A yeast infection (oral thrush) -Biting or scalding your tongue accidentally -Mouth ulcers (canker sores) that are usually white or yellow -Irritation that causes the papillae of your tongue to be enlarged -Medical conditions like stomatitis, leukoplakia, and cancer -Allergies and warts home remedies include -Avoid hot and spicy foods. -Try to drink only cold beverages and eat only bland, soft foods until the sore has healed. -You may also try OTC oral pain treatments. -You can rinse your mouth with warm saltwater or a mixture of warm water and baking soda. -You can ice the sore. If the pain hasnt reduced in two weeks or she develops any fever or the sore increases then it would be advisable too see a dermatologist too see if it an infection and antibiotics can be prescribed along with some mouth paints to soothe the pain

She need to take medicine for healing this ulcer. Give her soft diet or liquid diet till then. Take a consultation with me before it get worse. I can help you with this problem.