Orianthi is an Australian singer-songwriter, her debut single
According to You was a moderate hit in some countries back in 2009 (#3 on the Japan Hot 100, #8 in Australia, #17 in the US...) and her second single Shut Up and Kiss Me peaked at #11 on the Japan Hot 100 but didn't really make an impact anywhere else. She's played guitar for some big names like Michel Jackson, Carrie Underwood and Alice Cooper. Since then she's kind of faded away but she has a nice pop-rock style so she should sound nice with miwa!
edit: Oh! It turns out Orianthi played lead guitar on super heroine on ONENESS! Here's a pic of them together on instagram ->
https://www.instagram.com/p/zOENxJTMeT/ Here's another recent post of them together (2 weeks ago) ->
https://www.instagram.com/p/_FtU6pTMSB/