Downplayed: Mike turns into Michelle, and Alice stops hitting him/her, but otherwise ignores Michelle.
Alice has issues opening up to boys due to a traumatic incident in her childhood. But Michelle, even though only "technically" a girl, doesn't trigger those defenses, allowing Alice's deredere side to show through.
Alternatively, Michelle has a different personality than Mike (with the change in hormones making her slightly calmer). Or perhaps the sudden awkwardness of being female makes him uncomfortable with flirting with either sex, removing a significant obstacle to their friendship.
Alternatively, Alice does like Mike, but not in that way. She is attracted to Michelle.
Alternatively, Alice would have liked Mike all along if she'd ever noticed him in the first place, and as it turns out, being turned female by a plot device is pretty noticeable.
Gender Bender Antagonism. Alice is normally okay with Mike, but when he turns into Michelle, Alice takes an instant dislike to the new girl and tries to knock her block off. Maybe it was the boasting about the new breasts.
Alice and Michelle are already friends. When Michelle is turned into Mike, she/he takes the opportunity to start going out with Alice.
Subverted: Alice seems to take a shine to Michelle, but then starts acting as cold to her as she did to Mike.
Double Subverted: Because she mistakenly thought Michelle was going out with Mike. Once Michelle makes it clear this isn't the case (ew), Alice is cool with her again.
Parodied: Mike switches back and forth between his male form and Michelle, and Alice is aware of this. Yet she instantly switches from "Michelle's friend" to "Mike's Ice Queen" whenever the transformation takes place.
Zig Zagged: M Ike turns into Michelle, and Alice becomes his/her friend, but they soon quarrel and become enemies, then make up and become friends again, and finally settle on being frenemies.
Averted: Mike turns into Michelle, but since everyone saw it happen, it doesn't change how they feel about him/her.
Enforced: A TV show producer wants to have a show featuring Half-Identical Twins actors, and decides on this premise to make them Mike and Michelle.
Lampshaded: "I feel like I can share anything with you, Michelle. Not like that Jerkass Mike."
Invoked: Mike deliberately turns himself into Michelle in order to get closer to Alice and learn how to woo her.
Exploited: Dirk has figured out what's going on and blackmails Michelle not to reveal "her" secret.
Defied: "Even though I'm a girl now, I'm not going to take advantage of Alice's ignorance of the truth to fool her into befriending me."
Discussed: "That new girl, Michelle...she and Alice got close very quickly, didn't they?"
Conversed: "Based on the opening titles, and the fact that Alice turned Mike down flat at the beginning of the episode, I'm betting he uses this 'Michelle' identity to get close to her."
Deconstructed: Michelle enjoys her new relationship with Alice very much. But that relationship is based on a lie about Michelle's real identity. Mike hates his new female body and everything about being a girl except being best friends with Alice. So when a chance comes to regain his old body, he has to decide between being Alice's best friend and miserable the rest of the time, or having the body he's comfortable with, but losing Alice.
Reconstructed: Michelle finally breaks down and reveals the truth to Alice, who in turn admits she figured out what was going on some time ago. She feels that Mike should return to the body he prefers; while she still has no sexual interest in Mike, Alice has seen enough of his true nature in Michelle to want to continue to be friends.