You're just so used to seeing her with the head, same as me. It's like seeing picture of Levar Burton and finding it weird, or thinking 'man his eyes are so intensely wierd' then remembering that for many many years, you only saw him with the visor. In my case, and probably yours, literally the first time we saw these actors, it was as these characters after all.
That gets magnified if we find the characters attractive. Another example... Melora in Ds9 is more attractive than Grace Holloway in Doctor Who, from my perspective. It's because I would have found the angry scientist attractive in Ds9, and the character in Who not so much...also I did not even equate the two at first, because guest cast drifts by quite often. Yet this is the same person playing both roles.
Maybe this should also be seen as a positive in sci-fi fans...it shows that more often than not, even hormone addled teenagers may find a character attractive without that being purely defined by physical appearance. I am sure there's some theory out there talking about male gaze or exoticisation or something, but given there are many voyager fans mooning over chakotay or the J7 pairing, and this whole thread started because someone is rewriting two male characters sexuality because they possibly find them attractive (not to mention, in this world worried about toxic masculinity, isn't it a bit odd to pair off two male characters as homosexual simply because of a close friendship? See Julian and Miles for that too. It's something you don't see so often with female best buddies either. Well...outside of Deanna and Beverly fanfics I suppose.) I think most of that does not apply in this instance.
Bells was always hawt.