You're right, she could have been a concubine or wife. John de Mowbray may have even promised her the "known world"!
As her profile stands, she has no biography, no parents, no issue (legitimate or otherwise), and no sources. So right now, we just don't know.
My interest in her profile is that she is currently connected to two projects (EuroAristo and Magna Carta), where we do base what we're contributing on research and sources.
Someone loaded her profile. More than once based, as there was at least one merge. Perhaps someone knows something about her. Hence the question, have you seen anyone argue about her, mention her, suggest she existed and/or was connected to John de Mowbray?