The pair will clash in the main event, the women’s 400metres, which also features three-time Commonwealth Games gold medallist Tamsyn Manou (nee Lewis), who is chasing a hat-trick of titles.

Sheena, who lives in Melbourne, has been in Newcastle for the past three weeks training with Pirrenee at Glendale in preparation for the summer athletics program.

Adamstown-based Pirrenee is chasing the first of two A qualifying times of 51.50seconds in the 400m tonight to earn a spot for the London Games.

But she admitted her biggest hurdle might be overcoming the childhood obsession of beating her sister.

‘‘As little ones in juniors and little athletics all the time we raced each other and it was very, very competitive,’’ Pirrenee said. ‘‘So it will be weird racing each other again.

‘‘At the same time we are very competitive, but we know it’s what pulls us both through and makes us run even faster knowing that the other is there.

‘‘I’ve worked mentally to not focus on the other girls and to keep running my own race, but for some reason whenever Sheena gets back there it goes out the window and I have to regather myself and say she’s just another competitor.

‘‘It does throw you off a bit having your sister there, but it brings out the best as well.’’

Pirrenee made her Commonwealth Games debut in Delhi in 2010 as part of the Australian 4x400m relay team of Sally Pearson, Jody Henry and Olivia Tauro which finished fifth in the final.

After returning from Delhi scans revealed a stress fracture in her hip which ruined her season last summer.

But the 26-year-old said she was now at optimum fitness.

‘‘This athletic season we’re approaching is the first I’ve had a full winter of training, gym and track without any interruptions, so I’m very well prepared,’’ she said.

‘‘My training times have been on track for what I need to run to cement an individual spot at the Olympics. I’ve had four runs, so I’ve already had a chance to blow some cobwebs out, and I’ve posted a couple of quick times already.’’