His relationship with his enemies like Voldemort would also be affected. If Regina has some sort of power or influence over Harry, Voldemort might see him as an even greater threat or an easier target. Harry might also have different ways of defending himself, influenced by Regina's methods or the new environment he's in. For example, Regina might have her own way of dealing with dark magic that she teaches Harry, which changes how he approaches Voldemort and his Death Eaters.
Harry's relationship with the Hogwarts faculty could be altered too. If Regina has a particular stance on Hogwarts or the wizarding education system, she may influence Harry's view of the teachers. He might be more or less trusting of them. And the teachers, in turn, might view Harry differently because of his new family situation. Some might be suspicious of Regina's motives for adopting Harry, while others might be more understanding and try to help Harry navigate this new family dynamic within the context of his Hogwarts education.
His relationship with the teachers would also be different. Snape, for instance, might be more conflicted about Harry. On one hand, he's in Slytherin which Snape favors, but on the other hand, he's still Harry Potter. And Dumbledore would have to watch Harry from a different perspective, perhaps guiding him in a more subtle way to make sure he doesn't get too influenced by the darker aspects of Slytherin house.
Let's consider the relationship with Voldemort. In this fanfiction, Voldemort might see Fem Harry as a way to get to Narcissa or use her as a pawn in some way. But Fem Harry, with Narcissa's influence, could be more prepared to face him. Her relationship with the Order of the Phoenix would also be altered. Some members might be distrustful of her new family situation, while others might see it as an opportunity to gather intelligence from the inside. And Narcissa herself would have a very maternal relationship with Fem Harry, which would be a huge change from Harry's original lonely and often - unloved state in the canon story.
His relationship with Hermione might become more strained. Hermione, being very rule - bound and having a strong sense of right and wrong, might be very wary of Harry's new connection to Morgana. Ron, on the other hand, might be more accepting at first, but then start to worry as Harry shows signs of changing. With Dumbledore, there could be a whole new level of secrecy and trust issues, as Dumbledore tries to guide Harry while also being cautious of his Morgana - influenced powers.
His relationship with Ron and Hermione would be very different. Since he's been raised by the founders, he might be more aloof from the typical Gryffindor camaraderie. He could see Ron's insecurities in a different light, perhaps being less patient with them. And with Hermione, he might be more critical of her book - learning approach as he's been taught by the founders themselves.
His relationship with Hermione and Ron would be strained at first. They would be confused and a bit scared. But as they see Harry resist the dark side, they would become more supportive. With Dumbledore, there might be a new level of secrecy and mistrust at the start, but Dumbledore would likely keep an eye on Harry to see how he develops. As for the other students, many would be afraid and avoid him, but some might be curious and try to befriend him to see what it's like to be around the heir of Voldemort.
If Harry's wand were to fuse with another, say Hermione's, it could create a stronger bond between them. They would have to rely on each other more to understand the new powers of the wand.
Harry's relationship with Snape would be complex. Snape, who already had a difficult relationship with Harry, might be even more hostile. He could see Harry's connection to the Grim Reaper as a sign of dark magic. But as the story progresses, Snape might come to realize that Harry is using his powers for good. And Harry, on the other hand, might start to understand Snape better, seeing that they both have a connection to a power that is often misunderstood. With the other students, some might be afraid of Harry and avoid him, while others might be drawn to his new - found power and mystery.
Harry might become more confident. Rebbekah is a strong character, and under her influence, Harry could learn to be more assertive. He'd no longer be just the boy who lived, but a part of a different magical family with different values.
With Hermione and Ron, it would be very different. If Harry is de - aged, they might see him as a younger, more vulnerable friend. Hermione could become even more protective, like an older sister. Ron might be a bit confused at first but would probably still be his loyal friend. Their dynamic would shift from equals to something more like Harry being the 'little one' they need to look after.
Harry's relationship with Lupin would be very interesting. Lupin, being a werewolf himself, could act as a mentor to Harry. He could teach Harry how to control his werewolf side better. And this shared experience could bring them closer together. But at the same time, Harry might feel a sense of resentment towards Lupin, thinking that Lupin could have prevented his transformation in some way.