welcome to HealthcareMagic
At 3.5 yrs the reason of swelling of ankle is difficult to say but as per the reports you have posted there are few things which are increased like:-
-the WBC count
of 13 and the Lymphocytes 6.78 suggest that there is certain sort of infection in her body.
-secondly the ESR of 35 is also slightly raised and even it suggests infection .
The causes of infection can be any thing like even tonsillitis;fever etc so to relate that with the swelling is also difficult.I guess she still requires further investigations to rule out Strep infections and Rheumatic fever;to rule out tuberculosis
which is quite rare at her age.As for the vomiting
it can be as a result of acidity or gastritis
which can be as a result of long use of antibiotics so you can give her syrup-Ondem/Emeset 5 ml when she has vomiting or if she is complaining continuous nausea
then you can use it three times a day 1/2 hour before meals.