-The option buttons don't actually show up in a battle (since when did you see an array of buttons in Underverse or Glitchtale execpt RESET and OVERWRITE)? The buttons are a concept for fan fight invloving Blizzard as the "Frisk/Chara"

-Don't worry, Blizzard won't get incerdibly OP with Asriel's magic. It's not that the magic has been weakened, it's that Blizzard's stats aren't as high as Asriel, so it obviously won't be as strong.

Blizzard is an only child and lacks experience in Star Magic, so she has vulnerable spots too. Over time, she starts getting the hang of it and gains some Determination. She sometimes does a metaphor of herself having a black heart, but then,

a black heart does not always stand for an evil one.