What Causes Increased Sugar Levels In Diabetic Patients Inspite Of Using Medications?

Hello I have a question in regards to my mother in law who is diabetic. She normally controls it with medication. Although she has been off her medication for a few months. She started getting sick a few days ago. Symptoms were similar to that of the flu. We ended up taking her to urgent care Sunday night, and her sugar was 357. Normally it is around 140. She was given 500mg of Metformin to be taken 2 times a day. We started the meds sunday night, and are giving 2 times a day as prescribed. I tested her sugar levels at home a few times Monday. Just before she laid down is was at 240, and just checked at 2 am and it went up to 381. I have read that it can spike overnight that is normal. But that level has us concerned. I do not know what it is normally at that time of night. Normally you have increased thirst and appetite with high sugars levels, but she is the opposite. We did get her to eat some, but not a lot. We were wondering if we should take her to the ER now, or wait till morning and check it again after trying to get her to eat? I know everyone is different and may experience different symptoms.