Hi.. Thanks for the query.. As per your complain pain and redness in tongue can be due to dryness of mouth and bitter taste and dryness can be a side effect of the medicine she is taking.. You have not written the name of the medicine and just mentioned 10mg in the question.. There are certain medicines which can cause dryness in mouth along with pain ,redness and burning sensation and sensitivity to bitter taste and altered taste comes under BURNING MOUTH SYNDROME.. It is caused by certain medications like ACE Inhibitors which are used to lower high blood pressure.. I would suggest you to consult an oral pathologist and get her evaluation done alone with complete medical history.. In case if it is happening due to dry mouth change in medicine or reducing the dose by her treating physician can be relieving.. First of all to relieve pain she should start gargling with a numbing mouthwash containing Lignocaine.. In case of dry mouth Saliva substitutes containing methylcellulose can be instilled in mouth for lubrication. Saliva stimulants like sour candies, sugarfree chewing gums and lemon drops can stimulate saliva flow and help in increasing flow in mouth.. Drinking plenty of water can help in relieving dryness and inflammation causing redness.. Sucking ice pops can help.. Avoid hot and spicy food.. Hope this helps.. Thanks and regards..