Klass separated from partner of 11 years Graham Quinn in April after just six months of marriage.
It was subsequently revealed that the former couple would still be attending the nuptials of their pop star friends this month, but Klass is now believed to have given up her place in order to ensure peace at the ceremony.
"Myleene gave up her invitation to the wedding to avoid any kind of stand-off between her and Graham," a source told The Sun.
"Things are still raw between them and there's no way she'd want it to affect Marvin and Rochelle's big day. She's sent a gift and Rochelle knows she'd be there if things were different."
Humes and Wiseman are expected to tie the knot at Blenheim Palace, the 18th-century mansion where Winston Churchill was born.