Thumb sucking

Do any of you have a thumb sucker? My daughter has sucked her thumb since she was 1 year (after we took the bottle away). At first we thought she would stop on her own, now she's going on 5 years old & fixing to start school.. I'm afraid of bullying (yes, I know she's young but kids are bullying at very young ages). We talked with her pediatrician & she said to not say anything to her about it, that she would out grow it or a kid at school would say something & she would stop..