If they give her headaches, she might be too young to verbalise it but she wouldn't be too young to do something about it, like pull her hair out of the bands/clips.
My niece had a brain tumour, found at 21mo, that blocked the flow of her CSF and put her brain under very high pressure - she would have anything on her head for a few months before it was diagnosed - not a hat, a hairband, no bands, no clips, no nothing. She simply wouldn't tolerate it and would either remove it herself or cry until it was. Of course, we didn't know why until we found out about the tumour - but she made her feelings very plain that head stuff hurt her.
Having said that, I don't like the hair tautness in some of those styles anyway and wouldn't do that to a child.