If you know your character is a lot like a existing one, then, to make them unique, you want to do the following.
Deconstruct the Other Character
Deconstruct what made the other character work. Keep any traits you like. Improve upon what you don't.
Superficial traits like "lesbian" or "witch" don't get at the core of what makes the characters tick.
In her first appearance of the Owl House, Amity was the stereotypical popular girl who politely but snobbishly put down other people's feelings. Not too complex, but we learn a lot more about her as we go on.
For starters, even though she's arrogant, she's still above cheating. The thought of defeating our hero, Luz, by cheating is absolutely disgraceful to her.
She's also got a softer side, spending time at the local library to teach kids and share her favorite stories with them. Sweet stuff.
Underneath that all though, the core of her character is a deep-seated drive to always be the best. Perfect. Eclipse Lake is a great example of this because even after she's been accepted as part of the team, Amity still worries she's not perfect enough. A deep-seated insecurity that drives her every action.
Once you know the essentials of what makes this character tick, you can then say, "What do I like about them? What do I hate?"
Amity's arc in Season One is learning not to be a bully, and her arc is Season Two is learning to make amends but you've already mentioned you have a different plan for your character. She wants to see the world.
Great. How is that anything like Amity's arc? The farthest Amity's wanted to go is to see Earth, and that's mostly because of Luz, not because she's an explorer by nature.
That's a significant difference in character right there. Amity's mostly a shy book nerd with a gruff exterior. She's not the explorer type per se.
What Would You Improve?
Do you like Amity's personality? Her arc? Her character development?
If the answer is yes, try to incorporate some of those ideas into your character. Things like personal insecurity, the weight of expectation, a love of books, a need to achieve, etc.
Do you dislike any of her personality traits? What would you change? Did you think her development was rushed? Did you think she was too overbearing at times? Too controlling?
Then you can take those as lessons for what not to do with your character.
Characters Don't Live in a Vacuum
Lastly, even if your character was an exact copy of Amity at the start, she'd still end up a different person if she met different people and had different experiences.
Luz changed Amity because she was a spark of joy and freedom in her life. What if she met someone else or Luz had a slightly different personality?
Imagine Luz was quiet and shy rather than outgoing and fun. The dynamic between the two characters would shift into something completely unique.
If Luz was a less outgoing, befriending Amity might be a lot harder. Or easier.
But that one change would change the whole relationship. For example, if Luz never spoke up for herself, Amity might grow even more protective of her than she already is. This could push her personality to be more gruff and serious.
Which could lead to an arc about learning to relax, or lead to her character doubling down.
Then that dynamic changes how both Luz and Amity interact with anyone else.
It becomes a butterfly affect eventually making all the characters unrecognizable and thus fully unique.
That's the power of making a slight change.