Hi, Welcome to HCM.
I understand your concern. As you are aware that your mother-in-law's blood sugar is high (370 mg/dl), she is very susceptible to any infection such as cellulities. Controlling her sugar aggressively at this time along with antibiotics will certainly help her condition. Looks like she is also suffering from moderate heart failure
possibly due to long standing hypertension
She will need to be managed with drugs such as diuretics for her swelling and difficulty in breathing, digoxin
to improve the cardiac performance, ACE inhibitor
and/or ARBs to reduce blood pressure etc. Her urine output (kidney function) should also be monitored.
Based on the information you have given, her failing heart and high blood glucose
along with infection can have an additive effect on her condition. At this time she needs to be observed and managed very closely to prevent any worsening.
All the best. Hope this helps.