cloudkicker108 
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[@0d4n0bun4g4":](/1414603#comment_6035436
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>>1397233p
Sunset never openly expressed any genuine desire to join the band until near the end of the film; given that they've known her in the past to be more of an independent person (and that at the time she was dreading public attention for certain reasons), the hu-mane 5 likely just assumed that she wasn't interested in performing on stage with them. Even so, they definitely still saw and accepted her as a friend; In fact, they actually express their forgiveness to her again early on in the movie.
As for why Twilight would be nervous in trusting Sunset, keep in mind this is only the second reformation she has been involved in, and the very first that she had to manage directly. The first reformation she was caught up in was Discord, and we all know how skeptical of whole process she was then. By the time Starlight came around, she was the third reformation encountered by her. Twilight had already gained a great deal of experience in the matter from both witnessing Fluttershy handle Discord and interacting with Sunset since then, so she was much more confident in accepting Starlight's decision to reform. Not mention, of course, that unlike Sunset (who required a friendship beam to see the error of her ways), Starlight ultimately turned herself in to Twilight, which definitely would have had an significant impact on the Princess of Friendship.
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[@0d4n0bun4g4
>>1397233p
Sunset never openly expressed any genuine desire to join the band until near the end of the film; given that they've known her in the past to be more of an independent person (and that at the time she was dreading public attention for certain reasons), the hu-mane 5 likely just assumed that she wasn't interested in performing on stage with them. Even so, they definitely still saw and accepted her as a friend; In fact, they actually express their forgiveness to her again early on in the movie.
As for why Twilight would be nervous in trusting Sunset, keep in mind this is only the second reformation she has been involved in, and the very first that she had to manage directly. The first reformation she was caught up in was Discord, and we all know how skeptical of whole process she was then. By the time Starlight came around, she was the third reformation encountered by her. Twilight had already gained a great deal of experience in the matter from both witnessing Fluttershy handle Discord and interacting with Sunset since then, so she was much more confident in accepting Starlight's decision to reform. Not mention, of course, that unlike Sunset (who required a friendship beam to see the error of her ways), Starlight ultimately turned herself in to Twilight, which definitely would have had an significant impact on the Princess of Friendship.