I think she will outgrow it. Sometimes Bonnie will still do this and she is 17 months old. They all do it
and it can be aggravating at times.
You could get some bitter apple spray and spray your pants (*test first to make sure it won't stain) When she gets a mouth full of bad taste every time, she may quit.
You could use a squirt bottle with water, but she is so young, maybe someone else can make a suggestion.