She has been named in a team of 12 for the Olympics and is determined to fight her way into the 4 x 200m relay squad, where she is currently fifth-ranked behind Hind, Gessler, Palmer and Wellington teenager Samantha Lucie-Smith.
"June 4 is the cut-off for that 4 x 100m team to get the nod from Fina, and even if we're bumped to 16th we've been told we'll still be going because 16 teams can line up in the relay," Marshall said yesterday during a few days off at Mt Maunganui.
"Breaking the record we set in Delhi shows we're all racing faster than we were then and potentially there's still more there."
Marshall will continue to train on Auckland's North Shore as if the 4 x 100m relay team has qualified but has plenty left to prove to force her way into the 200m lineup.
Lauren Boyle won the national title in 1m 58s, with Hind second in 1m 58.69s. Less than 0.16sec separated Gessler (2m 00.07s), Lucie-Smith (2m 00.12s) and Marshall (2m 00.23s).
"I'm the fifth girl out of five right now but there's more time trials to go and the fastest team will be the one that lines up on the blocks. It's competitive and will be for the next few months but I want to be in that team and will give everything I can to do it. I don't mind who I bump out, as long as I get to swim."
Marshall was thrilled with her freestyle and backstroke golds, as well as the relay record, but knows she let slip a chance to medal in the 200m. "That one race was disappointing, and on form I know the 200m could and should have gone better. But it was one bad race, not a bad meet."
Marshall puts the fact she's setting personal best times down to national high performance coach Mark Regan, who has been coaching her for the past 12 months, adding more volume to her workload and building an impressive aerobic base that is paying dividends in the pool.
"Mark's training has tended to be more traditional," Marshall said, "with long kilometres and different energy systems. Two years ago for the 200m free the last 50 would feel shocking and I'd be dead, but now with all the training under Mark and the aerobic threshold work we're doing the last 50 feels like I can still go.
"It reminds me of the programme I had when I was still in Tauranga with Clive Power. He and Mark are very similar in personality and coaching style."
Even when she's away from the pool Marshall never completely relaxes, waking instinctively every morning at 6.30am without fail. She's enjoyed time back at the Mount this week with parents Shane and Dawn, who were poolside in Delhi 18 months ago as her relay team snatched silver (200m) and bronze (100m).
They'll head to London in July, although with the swimming a hot ticket item and reportedly already over-sold, Marshall's parental allocation of one ticket isn't going to satisfy everyone.
"One of the other boys in the team has a crew of six (supporters) going to London, so apparently they're going to all draw straws when they get there ..."