Did the blood work include a serum chemistry screen?
Has the complete blood count been repeated to see if the white count has changed?
Were heart and lungs checked?
Has an x'ray of the chest been done? This would show if there are sings of lung disease or if the heart is enlarged.
Have x'rays and/or ultrasound of the abdomen been done?
You need a diagnosis to determine appropriate treatment. It doesn't sound like you have one yet. Sometimes an accurate diagnosis is difficult to determine. More dagnostic tests to look at the chest (lungs/heart) and abdomen (GI tract, liver, kidneys, etc.) and a repeat of blood work are a reasonable place to go.
A cough with a foamy exudate indicates a problem in the lungs and/or heat. This could be a result of the vomiting if she aspirated some of the vomit into her lungs for example. It could be caused by a separate problem that may have become apparent after the GI upset. Coughs are often slow to resolve.
The repeat CBC is important to determine if the presumed infection is getting better. A repeat chest x'ray may also be indicated. If the coughing continues after the antibiotics, a culture for bacteria and sensitivity to antibiotics would make sense. Some veterinarians, particularly in specialty practices, can look at the inside of the trachea using an endoscope to see if the cause can be determined.
10 pounds is a lot of weight to lose within 2 weeks and would make me look for a specific cause if she does not gain it back quickly after the vomiting/diarrhea stops and she is eating again.
It sounds like she has a vet appointment scheduled in a couple days. If she has not improved significantly by then, other diagnostic options should be discussed.
Let me know if you have follow up questions.