Selena Gomez's friend Mirtha Michelle is ''very honest'' with her about Justin Bieber.

The 'Letters, to the Men I Have Loved' author isn't concerned about the 'Come & Get It' hitmaker, who rekindled her on-again, off-again romance with the 20-year-old star last month following their latest brief split in April, because she thinks the 21-year-old singer is ''so mature for her age.''

Asked if she gives relationship advice to Selena, the 30-year-old actress told E! News: ''Selena is actually a friend of mine, so she's a very sweet girl. Although she is younger than me, she's's so funny because when I met her, I don't really watch TV and I know anything that's happening, when I met her I thought she was older. I thought she was two years older than she was. She's so mature for her age. She'll be trying to give me advice. I'm like, 'Hold up, I wrote a book!' ''

Sources close to Selena recently claimed her pals are worried she is ''hypnotised'' by the 'Baby' hitmaker and ''doesn't seem to care that he spends time with other women.''

But Mirtha says she is always honest with her friends when it comes to their relationships.

She said: ''I am very honest. I tell them how it is. 'Hey, maybe he's not that into you!' Because someone needs to tell them that. Sometimes we talk to our friends and our friends just cover up the sun with a finger. You can't so that. You have to say the truth, you have to be honest. 'Hey, he's still seeing his ex girlfriend? Is that what you want in your life? No, you don't.' ''

Selena attended Mirtha's book launch in New York City in May.