Your wife (and you) should practice good handwashing techniques, and be sure to encourage your daughter to cover her face when coughing or sneezing (if she is) and encourage good handwashing with her, too.
Usually if someone has been on antibiotics for 24 hours or more, they are not contagious.
Did she have strep throat, diagnosed by culture or rapid strep test? If she had a run of the mill sore throat and the doctor just gave her antibiotics, unfortunately she could still have a viral illness causing the sore throat. Antibiotics won't help that, and she'll be contagious anyway.
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