I have a lot of experience against Bayo and I believe this is 50-50.
This is one of those matchups were each char has a very specific role: if we space correctly and reduce her chances of starting combos ,we win; if she is able to start her combos consistently, she wins.
Pros
DFS beats her ground side B so if Corrin mixes up their shots, it can heavily stops her approach.
Our hitboxes rule as always, especially nair.
Dash attack works great against witch time. Its just situational but is another option we have.
Just as we have to be careful of witch time, she has to be very careful of our counter, especially near the top.
She makes damage quick but then she has difficulties getting the kill, which means rage throw kills for us.
Cons
Bullet climax beats our dfs so Bayo its better for her to play a more campy game and force us to approach.
Witch time, witch time, witch time...
She has way more gimping options than us and her recovery is much more better
Don't underestimate her combo potential. You can be winning by more than 70% and she just needs one good hit confirm to get a combo to a kill.
Tips
My main advice is always try to land away of her and never, I mean NEVER, land doing an aerial. Witch time is its strongest when it activates in situations where we are landing and she is on the ground. After you have conditioned the opponent into thinking that you will never land with an aerial, then that's when you do a landing nair or fair, just remember to be very cautious and mixup your landings.
If a player likes using a lot witch time, force her to use it when both chars are in the air. Its very hard for Bayo to confirm or do big damage if she is in an uncomfortable position.
She is a damage-racking machine. Don't get confident if you are ahead one stock, keep playing cautiously and always control space.
Stages
Platforms are great for us and helps to prevent Bayo from spamming bullet climax. The DL mixups are most effective on platforms stages like Battlefield and Dream Land anyways.
I always ban FD as it allows her to control space more with her b move.
In general the matchup at the beginning feels like is bad for us but actually is not that bad, is just that witch time is so dangerous and rewarding that we have to play extremely defensive and use much more our throws than in other matchups.