How long did your parents live in denial over you being trans? {this is a bit of a rant/vent as well}

I have been giving my mom bits about me being trans. I told her that I am trans and I told her that I am seeing a gender therapist to get on hormones just today. She has not talked to me almost all day. She came in once to give me her response to the letter about hormones and that is it. I am worried that she is in a place where she is thinking "this is a prank", "this is for attention", or something like that. I worry that when I start T she will flip. I haven't told her about my name or pronouns yet. I don't know what she'll say. Note that I am 18 but I live with her and am a senior in high school. Graduation is in early June.

Update: My therapist informed me today that my mom called her and said it confused her and shocked her.