70 percent sure its from where's my beefalo and other mods that add map icons... I disabled that mod and never used any other mod woth similar function and havent missed an attack. I can confirm the not missing part 'cause i use simple health bars that have dmg indicators.
Im having the same issue. I noticed that ypu can still fight her but not land any hits, i jist kite her until enrage stage then use panflute. After that i can hit her normally, its only on larvae stage where you really cant hit her, just lengthens the fight by a couple of mins or so.