hairy –
(Google says calvepen is penicillin v)
That’s no more “strong” or harmful than amoxicillin (and arguably it’s a better choice for throats too)
Isn’t magic though and (even if this is bacterial and sensitive to the penicillin) it’ll be a few days before she’s right; the antibiotic is there more to prevent complications than to make the sore throat better any faster. (if it’s genuinely a severe tonsillitis, that’ll be a few more days).
She has a very sore throat and so doesn’t want to swallow stuff – don’t fret about not eating. See if you can get her to drink something like milk if she won’t eat soft food. Those sugar-free lollies are quite good value too, I think (help keep her throat lubricated when she swallows)
re ibuprofen: I stick by what I said: if she needs it (to control temp), I’d rather give both that and paracetamol than risk a febrile convulsion (I’d still call them rare/unlikely, but are certainly possible). Only time I WOULDN’T give ibuprofen regularly would be if she’s not drinking & getting dry – if she’s peeing plenty, that’s OK.
If you want to be posh, weigh her (should be about 16kg or so if she’s 4) and give her 7.5mg for every kilo of her weight (so, about 120mg or probably 6ml if it’s 100mg in 5ml) 4 times a day. Alternative would be 10mg per kg three times a day (about 160mg or probably 8ml per dose)