YouTube to MP3 converters are fine for archival purposes but I wouldn't recommend them for music. YouTube in itself compresses the audio a bit when encoding it, and the MP3 conversion compresses it even more aggressively since MP3's an incredibly lossy format, so usually what you're left with is a tinny mess.
Ripping the file directly from Bandcamp is a better option in general, but in this case since she has it set to name your price I'd suggest not using this as a rehearsal for your Idol Corp. audition and instead paying her what you can afford.