How do I tell my mum that I'm serious about being bisexual?

hmm well when i told my mom that i was bi she acted too well about it? later she told me she wasnt comfortable and that she would need some more time getting use to it....when i came out i was already dating my girlfriend..so i guess that kinda got rid of the "just a phase" saying but you should sit down with her and explain to her that your serious about it...if u told her the truth and told her you are a lesbian then i think she would then take it more serious though but i mean its your choice...good luck :)