Reports have suggested that Timberlake has been secretly dating Kate Hudson for the past year.
A source told America's OK! magazine: "Jessica knows she and Justin are happy and there are no problems. But she wanted to get a female perspective on the best way to handle all the rumours about him with other girls.
"Scarlett told her to ignore the speculation and concentrate on the relationship."
The insider added that Biel now wants Johansson and boyfriend Ryan Reynolds to accompany the lovers on a date, saying: "Jessica has suggested that when she gets back from filming her latest movie Easy Virtue she could teach Scarlett to play golf so they could double-date with Justin and Ryan."
Johansson was rumoured to have dated Timberlake last year but refused to confirm that they were an item.