I made two edits, adding Evie Anderson as an artist to The BeauBowBelles. The first simply listed her as a vocalist, the second adding 'cello' to the list of instruments.

https://musicbrainz.org/edit/45054949
https://musicbrainz.org/edit/45054950

When these are displayed on the group's relationships page, she is listed twice, once per instrument. However the other group members are only listed once, with their entry showing multiple instruments:

https://musicbrainz.org/artist/423a1737-6181-45ba-a614-857fa16c1140/relationships