There's is no infection that can kill you.
She may have a sore throat, or tonsillitis, which defines the tonsils in your throat.
They either are viral, or bacterial.
If Bacterial, she must see a doctor for peniciilin, or other medications to cure it.
If that's not the case, she has an abstance.
Forgive me if I spell it wrong, but it indicates infection behind the throat.
This you must see a doctor immedietiely.
This is what I know. Hope this is useful

Are you sure you're talking about an infection and not an allergic reaction? You said it makes your "throat go big." If she has a severe enough allergy, she can go into what is called anaphylactic shock, where her throat can swell closed, her tongue can swell, she can get hives or a rash on her skin. That can be life-threatening if she doesn't get treatment in time. Is that what you're talking about?

Also, referring to the post before: it's not true that infections can't be life-threatening. Most in the throat will not if the person has a healthy immune system, but there are a lot of infections that can kill you, especially if they aren't treated.

she may have mono. idk whats going on with me i have something but its lasted for a week now it sucks and i have a swallen lip, swallen throat and i cant swallow anything without meds n antibiotics isnt working. but my ears are hurting. i dont have any of the other signs of mono. does anyone know what i have?