Should I reveal my alcoholism to a fwb?
Maybe. Why would you not reveal that?
She will misunderstand me.
You shouldn't lie to your fwb about that. Alcoholism is serious and you need to reveal that and get help.
She won't understand me if I tell her, she will abandon me and I won't be able to live knowing that I won't have her again.
But she will eventually find out and will be hurt that you kept it form her. Being honest is important for a relationship to thrive otherwise it just leads to more problems.