It's probably simpler to not animate the character breathing while talking. People don't breathe normally while talking anyway as we intake & expel breath much faster & often during the small pauses we take in between words.
Like I mentioned on Discord, you would be better off just creating some talk animation frames & then setting the play order to random - or use the new lip sync feature (seems I will need to write up a new tutorial for that as it has randomly vanished without a trace from the wiki).
The other alternative would be to temporarily swap out the character with a headless version & teleport an npc character that contains just the head & make that talk instead.
You could also try to force frames with Lua script, but my experience with that has shown me that it doesn't always work - especially more so, since the last update of the engine.
If you own Spine, then you could use Spine character models, but I don't know if Simon has programmed in support for runtime to switch out sprite parts & trigger specific keyframe animations - I know this is possible with some engines that support Spine, but you know...