Hi, thanks for your query.
White patches on the inner side of lower lip are most commonly due to thrush
But there are other possibilities which may be as follows:
-It could be bacterial or viral infection
-Accidental bites in lower lip
-These may represent the openings of minor salivary glands found throughout the lips.
I suggest that she should be examined by a pediatrician
for exact diagnosis and treatment.
Hope this solves your query.
I wish her a speedy recovery