Brand was pictured kissing Schuller at a cafe in Hollywood last week, reported Sun Online.
Mother-of-one, Schuller, who has been Brand's make-up artist and hairdresser for almost ten years, is a London fashion graduate.
"Nicola's been Russell's good friend for ears and was his shoulder to cry on through his divorce from Katy Perry, and splits from other women. She created the style he's best known for - his spiky back-combed hair. He has a lot to thank her for.
"But in the last few weeks things between them have got a lot more hot and heavy than just friends. The way they were kissing in public speaks for itself," a source said.