Everyone always thought that BaeRyS were the go to example of "friends acting gay for the yuribait" but Bae's strange behavior about it makes me think deep down something happened and both IRyS and Bae actually kissed causing Bae to develop romantic feelings for IRyS as this was her first kiss.
I am no psychologist but it seems Bae is trying to not think about it as she doesn't want to ruin her friendship with IRyS and because of this, she has been behaving the way she has been behaving (telling the Chat to shut up) and it's like she's running from how she actually feels about her friend.
IRyS is a type of girl who will at best will just fool around with a girl but would never settle down with them and needs a man to take care of her