One reason could be his mystery. Gaara has this air of mystery around him, which can be really attractive. Also, his power as a ninja might be appealing to her.
There are several reasons. Gaara's strength is obvious, and female Naruto might admire strong people. Also, his transformation from a lonely and feared person to a respected leader is inspiring. His unique appearance, with his red hair and those kanji on his forehead, could also be part of the attraction. Moreover, his loyalty to his village and friends shows his good character, which could easily make female Naruto have a crush on him.
It could be the influence of a powerful enemy or a dark power. Suppose there is an enemy who has the ability to manipulate emotions or a dark power that corrupts Naruto's mind. This could lead him to change his personality and become more like Gaara. For example, if the enemy makes Naruto feel alone and unloved, he may start to develop the same cold and distant behavior that Gaara once had.
Well, in many fanfictions, it might start with Gaara noticing Naruto's unique strength and unwavering spirit. Naruto's ability to reach out to others, even his enemies, could be very appealing to Gaara. Maybe during a joint mission, they have to rely on each other, and Gaara starts to see Naruto in a different light, gradually developing deeper feelings as they spend more time together.
Often, older women can be more nurturing. If a girl lacks that kind of nurturing presence in her life, she may be drawn to an older woman who seems warm and caring. The older woman's confidence in social situations and her ability to handle various things gracefully can also be very appealing to the girl.
One reason could be friendship. Gaara and Naruto have a special connection in the original story. In fanfiction, this connection could be deepened, and Gaara would save Naruto because he values their friendship. Just like Naruto once reached out to Gaara, Gaara would do the same for Naruto when he's in danger.
One reason could be the extreme pressure of being Hokage. He has so many responsibilities, like protecting the village from external threats and managing internal affairs. It might all become too much for him to handle, leading to a breakdown.
One possible reason could be a deep emotional bond. Maybe Gaara has seen Naruto's unique strength and kindness, which makes her feel a strong connection. It could also be due to a sense of protection. Naruto might have been in situations where he was vulnerable, and Gaara's possessiveness is her way of ensuring his safety.
Well, her intelligence is a big factor. Hermione is known for being extremely smart in the original series, and that's very attractive. In fanfiction, characters might be drawn to her quick thinking and vast knowledge.
One reason could be that he has deep feelings for her. He might not be used to having such strong emotions for someone and this possessiveness is his way of showing how much he cares.
In such a fanfiction, their relationship could develop gradually. At first, female Naruto might be too shy to show her feelings. But then, through shared experiences, like fighting together against a common enemy. Gaara might start to notice her in a different way, and their relationship could start to grow deeper.
One sign could be that Tsunade is overly protective of Naruto in the fanfiction. She might always be looking out for him more than she does for others. Another sign could be that she gets flustered or blushes around him, which is a common indication of having a crush.