BEIJING, July 9 -- Lindsay Lohan has been given a $22,000 "commitment" ring by girlfriend Samantha Ronson. The 'Mean Girls' actress was taken shopping by the DJ last week to celebrate her 22nd birthday and was thrilled when Sam splashed out on the stunning piece of jewellery. A source told Britain's Daily Mirror newspaper: "Sam took Lindsay shopping as part of her birthday present. Although Lindsay is the major breadwinner, Sam has her own money and is very proud. "It's not an engagement ring - simply a token of her commitment. Lindsay is thrilled and she and Sam are very content." Yesterday, it was revealed Lindsay's partying ways have been curbed by her girlfriend.

Lindsay Lohan

A source said: "Sam and Lindsay are inseparable. Sam has been a really good influence on Lindsay. There is no one else special in Lindsay's life apart from Sam but it has taken her a while to feel like she can talk about their relationship. "Lindsay hasn't dated any men since she started hanging around with Sam, and there has hardly been a day in the last two months when they have been apart."

Lindsay - who spent time in rehab last year to be treated for alcoholism and drug addiction - spoke about her relationship with Samantha, the sister of super-producer Mark Ronson, as she celebrated her 22nd birthday last week.

The actress said: "I just want to live a happy, healthy year, continue on the path that I've been on and be with the person that I care about, and my family."