It seems to be 'Sucker's blister' ;due to continuous sucking of toys by baby.
If your granddaughter has white blister on outer,upper side of gum it is usually Bohn's nodule. Exact cause is not known. But are thought to arise from remnants of the dental lamina
or from heterotrophic salivary glands.
As you are saying ,baby cries during bottle feed, make sure she is not having thrush
Thrush will usually involve other areas too like tongue, palate
Sucker's blister and Bohn's nodules disappear within few days but thrush will definitely require treatment.
To be on safer side,consult pediatrician
to rule out thrush.