Responses
i think you're talking about the evil lady's hero
the evil lady's hero http://www.mangago.me/read-manga/the_evil_lady_s_hero/
It’s called “The Evil Lady’s Hero” :D
Thanks everyone for your answers ! It is exactly what I was looking for :D
Looking for a manga about a girl who is a water mage (and doctor) and was reincarnated in a side character. She met with the ML who is a very powerful fire mage and has some issues to contain the magic. So she helped him with the water magic. She finally met with the heroine who has a bf cheating on her and have hard times because of that.
I don't remember the name of it.
So help me to refresh my memories, please !