Sunset Shimmer normally likes to go in blind with her letsplay videos so her anger may be half frustration with how difficult Asriel is and half being reminded of her time as Sunset She-Demon due to how similar they are both being characters get corrupted and infused with powerful magic after absorbing powerful magic items Asriel with the six human souls and Sunset with the Element of magic (also coincidentally the human souls and elements of harmony are both six in number and based on positive human traits). btw because of the similarities sunset cries at the end of her Undertale playthrough when you can choose to give Asriel a hug, fyi she gave him a hug:).
 

 
 
Credit goes to the-butch-x for the original game stream template.