At a time when some people can't work because of coronavirus restrictions, or downturn in travellers to Canberra, the 17-year-old spotted a lady standing at the checkout.

"I had gotten the pay that day and I sort of looked around and was like, 'It's pension day' and told dad I wanted to surprise this lady and buy her groceries," the 17-year-old said.

Waiting in the checkout queue, Ms Lawson asked an elderly woman if she could step ahead of her, as she only had a couple of items to purchase.

She took the opportunity to hand the man at the checkout enough cash to cover the woman's groceries.

Ms Thomas, who has just graduated year 12, said her father and the man at the checkout were both a little shocked but went along with the plan. "I just thought it was such a lovely thing," her father Steve Thomas said of the encounter.

He caught the community's attention with a Facebook post about his daughter's good act.

"With everything going on in the world at the moment it's nice to have something else to focus on," Mr Thomas said.

The woman later caught up to her to thank her.

"She saw Lilli and just smiled at her and sort of beckoned towards her," Mr Thomas said.

Lilli said: "The look on her face was so sweet, she was so happy."

Lilli has also recently pulled off another act of charity, convincing Mr Thomas to find another way to fund those in need.

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"Recently I've sort of been convincing dad to give 5 per cent of his seller's commission to a charity of the seller's choice," she said.

Mr Thomas was impressed by his daughter's pitch and has agreed to start doing so for three months.

She attributes her philanthropic streak to her father's involvement in charity throughout her life.

Lili had just started work at her father's real estate agency Edge Real Estate, and handed the cashier about $180 to cover the woman's groceries, leaving the woman with extra change.

"There was some good karma there," Mr Thomas said, noting the woman had first let Lilli ahead of her in the queue.

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