Certain imports of popular brand toothpastes might contain lower quantities of fluoride than the recommended quantity depending on the country of manufacture.
-Children ages three years and under should use toothpaste with a fluoride level of at least 1,000ppm (parts per million).
-After three years of age, children should use toothpaste with a fluoride level of 1,350-1,500ppm. Most adult toothpaste fall within this range. The level of fluoride in every toothpaste can be found on the toothpaste pack.
The recommendation is based on the optimum values of fluoride that can help prevent tooth decay.

Use age appropriate toothpaste. It's not the brand of the toothpaste that matters but the amount of fluoride it contains.

Take her to see a dentist to exclude oral infections, decay, gum disease etc. If it's still persistent you may need to see a paediatrician as well to exclude other causes