I'm not sure which ones do you count as her solo originals. But personally I will only count Reflect and Ash Again.We got 8 original songs (not even counting big group songs), of which 5 were solo originals.
Full Color - good song, sadly was never released
Blue Horizon - more of an intro song, I don't think Gura herself even consider it as her "original"
Tokyo Wabi Sabi Lullaby - good song, but it was a collab with HoneyWorks in which she only provided the vocal
GIVE UP 今世 壊 - I bet most people forgot this song even exist, anyway song was kinda mid and it was a collab with Dye Iwasaki in which she only provided the vocal