["Someone gave my husband and I tickets to a concert and we can't wait to go, but my sister really loves the band we're seeing so I feel bad going too."]
Yea that is kind of a weird situation. I am sure she would want you to have a good time though.
Someone gave my husband and I tickets to a concert and we can't wait to go, but my sister really loves the band we're seeing so I feel bad going too.