To think nursery worker should not tell my daughter not to suck her thumb?

[chaosisawayoflife]

Genuine aibu.
Dd is 3 and is a big thumb sucker. She has been since age was in the womb and it gives her a lot of comfort. I have never told her not to or tried to discourage her.
I picked her up from nursery today and she said 'I'm not allowed to suck my thumb, am i?'. I asked why she said that and she told me that one of the nursery workers had told her off for sucking her thumb.
Now, I would understand it was interfering with her trying to say or do anything but it never does. She only really sucks it when she is having a quiet few minutes or if she is nervous, tired or concentrating on a story or something.
I'm a bit cross about this as her thumb is her security, her comfort and an instinctive, reflex action but I genuinely don't know if aibu to feel this way and whether I should say something.

Theres a lot of things people do for self comfort, but it doesnt mean we dont discourage the unhygenic or gross ones, or the ones that have a high risk of deforming the face

I think I said it was gross. I also said I had a ds who sucked his thumb constantly and I battled for years to get him to stop. I know it's hard (been there done that) but it doesn't make it any less gross.