Hmmm. I think Vanessa would have less credibility if she couldn't write songs, and only recorded those written by others, but she is a very gifted songwriter and has made many exceptional self-penned records.
Since Vanessa can write her own music, does that mean she should be close-minded to an entire population of other songs or songwriters? I personally don't think so. If Vanessa respects the artistry of a song not penned by herself, and she can relate to the song and feels intimately about it, why shouldn't she be able to perform it? I think Vanessa would be doing herself a disservice if she did not even consider the work of other gifted songwriters.
Also, I believe it shouldn't matter whether a song is a cover or not. Is it only okay for Vanessa to record music written by others only if someone else has recorded it before? I don't quite understand the logic in that. If Vanessa is producing a song, I believe she'll try her best to make an intimate, fresh, respectful recording no matter if the song is a cover, written by someone else, or a Carlton original.