well it's a manifestation
I interpreted it more as in she was too distressed to properly be able to focus on the healing magic, something she has presumably never used and learned once long ago. Whereas the other magic was her gaining some of her composure with her determination, as well as relying on the despair of the idea that she may lose her sister (which we already know is a catalyst for awakening one's power) ╮(￣▽￣)╭
Not out of mana but too shaken, special magic is instict and easier to use, plus hers used life force instead of mana
hold on let me get this straight, mc couldn't do healing magic cause she was out of mana but instead she could go and do time altering magic that is said to not only not exist but can only be used by gods?! Dude make up your fucking mind!! Like how the fuck does that make ANY sense?!