Singing at Sister's Wedding Controversy

I (F17) have an older sister (F23) who got married last weekend. The wedding had

all of the extended family from her side and the groom's, and we both have big families so

the wedding was pretty big. During the reception, my aunt had requested a song from the

DJ and went up to the microphone by the dance floor and started singing along to a Katy

Perry song. I assumed she just spontaneously did this and that this wasn't preplanned.

I just assumed this was something any guests could do as a bit later my other sister did

the same thing with a different song. Afterwards, I requested a song (Yellow by Coldplay

if that makes a difference) and sang it. My sister (the bride) was giving me a