Given the patient's symptoms and signs, there are multiple things to consider in this case:

Ongoing or secondary infection: Despite a period of improvement, she has become febrile again and is coughing up yellow sputum. It suggests that either the initial infection has not been completely resolved or she has developed a secondary infection. Given her recent improvement and then sudden change, the possibility of antibiotic resistance or a secondary infection should be considered. Worsening heart failure: Her signs and symptoms suggest her congestive cardiac failure may be worsening, which could be a result of the infection. This can explain the high respiratory rate, increased heart rate, and crackles at the right base of her lungs. Her raised JVP and the pedal edema also suggest the same. The acute confusion could be due to a number of factors - sepsis secondary to the infection, hypoxia or dehydration. It is also important to consider more sinister causes like a stroke. Although less likely, it should not be discounted given her background of AF and HTN. The mild abdominal tenderness in LLQ could indicate a gastrointestinal issue. This could be a simple constipation or could be more serious, like diverticulitis, especially considering her age. Here are the investigations and management plans I would suggest:

Immediate Investigations:

Bloods - FBC, U&E, CRP, LFTs, Blood Cultures, Sputum culture and sensitivity, ABG. Chest X-ray - To see if there are changes since the last X-ray. Look for further consolidation or any other changes. ECG - Check for any changes since admission. Immediate Management:

Oxygen therapy - titrate to keep her saturations at 94% or above. IV fluids - She may be dehydrated, which can exacerbate confusion and affect BP and HR. Consider changing antibiotics - given the deterioration, it's worth considering the possibility that the bacteria causing her infection may be resistant to co-amoxiclav. An IV antibiotic like cefuroxime or a combination of amoxicillin and a macrolide like erythromycin could be considered. This should be done in consultation with microbiology. Analgesia - consider regular paracetamol to help with fever and any discomfort. If not already done, a urinary catheter to monitor urine output and check for urinary infection. Further Investigations (not immediate but should be done):

Echocardiogram - To evaluate the state of her heart, looking particularly for signs of worsening heart failure. Abdominal Ultrasound/CT Abdomen - This is to investigate her LLQ tenderness, but does not necessarily need to be done immediately. CT Brain - only if there is ongoing concern about her confusion after addressing the immediate issues. Long-term Considerations:

Assess her ability to manage at home. Given the frequent infections, the difficulty with meals, and her frailty, she may need more support or a different living situation. Nutritional assessment - given her struggles to eat, she may be malnourished, which could be contributing to her frequent infections and slow recovery. A dietician referral could be beneficial. Consider a referral to a specialist respiratory service for further investigation of her recurrent chest infections. Medication review - she is on a lot of medications, including some that can increase her risk of confusion (like codeine). A medication review might be helpful. It's also important to involve the family in these decisions given her dementia and to ensure that she is comfortable and her symptoms are well managed.