Well, sounds like she just needed an excuse.

Be glad she didn't give your dad the ultimatum, "Either the kid goes or I do!" You coulda been orphaned.

What happened at this first meeting? Are you still living at home or super close where she feels like you’d be an interference? She’s still a bitch for handling it the way she did. Even if she was just looking for an excuse. That’s not fair to place on the kid though, no matter the age. A grown child is even worse.

do you perhaps live at your fathers place ? at 28.....

Stepmom implies they’re already married. She’s willing to divorce your dad because of you, a 28 year old who must live a ways away if this is the first time you’re meeting? She’s making excuses.

Either you’re leaving out a chuck of information or she wanted to leave your dad all along. Either way sorry.

Sounds like you did your dad a favor.