How was she tricked? She's told of the drug from the very beginning and it's not physical attraction that made her fall in love with Corrin. She flat out states that female Corrin isn't her type.
I went back to transcript more from the video:
Soleil: There's no other person, no other guy that makes me feel like this. Ever since that day where I saw you as a girl, I really fell for you.
MC: So, what? Does that mean that you fell in love with just the girl me?
Soleil: Uh huh.
MC: Uh huh? Oh come on.
Soleil: Oh don't worry. I like you even if you look like a male. I love you. When I had that magic powder, I saw a bunch of other people that looked like girls, but none of them got me excited or got my heart racing like you did. Heck, my heart is beating right now. Touch my chest and see.
MC: No no no no.
Soleil: Why?
MC: Come on, even if we're going to be husband and wife, I can't just touch a girl for the hell of it.
(snip because I don't feel like transcribing irrelevant dialogue)
MC: Oh, and don't cheat on me with another guy... maybe I don't have to worry about that.
Maybe "tricked" isn't the right word, but nothing offered here as a better translation implies that she genuinely is attracted to men. Yes, she does say that Female MC doesn't really get her weak-kneed upon meeting, but she also admits that she only fell in love with him after the potion. And there are so many awkward cues in there that don't really present her as legitimately straight. The first line is clarified from "no other person" to "no other guy" that makes her feel that way. She says that she like him
even if he looks like a male with the implication that looking like a male is ordinarily a problem, just not for him now. And then there's finally the joke about how he guesses he doesn't have to worry about her cheating on him with another man because she
actually likes girls.
None of the previous FE incest relationships were this risky and I doubt Nintendo would start now that the series is gaining in popularity. I don't find her advances on her mother genuine so I also don't find the very same advances on other girls genuine. I think it's more likely that she just has a cute girl issue, especially since the game has actual gay relationships.
It doesn't affect her in battle, that was a mistranslation and the video clears it up.
I just don't understand what the non-sexual interpretation is for her "cute girl" issue. What else is it? She says that she gets weak in the knees and aroused... cute girls get her going. And sorry for ignoring the clarification about the battle, but it's still describe as a problem she wants to get over. After a battle she literally fell over because a cute girl from the village came up to her. It sounds to me like she's being describe as a lesbian with a comically high libido. What's the alternative explanation to explain her reaction to cute girls that would imply she's not actually a lesbian?