The 19-year-old took 1500m silver at the National Under 23s Championships as one of the youngest runners in the field.
The performance helped to earn her a place at this weekend’s Olympic trials to decide Team GB’s track and field squad for Rio.
Mari has been invited to compete at both 800m and 1500m, but has opted for the longer distance.
Coach Bill Winter said: “Due to the standard and ferocity of competition, it will be difficult to progress beyond the heats, but this will not faze her and she is up for the challenge.”
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Her confidence will be sky high after an excellent performance at Bedford where she ran as a first year U23 in the British Athletics system.
The event came just a few days after clocking the latest in a long list of personal bests this season, knocking 0.15secs off her 800m mark at a meet in Watford, lowering it to 2min 07.28secs.
Back at Bedford, with no-one to take up the pace, Mari bravely took up the running after the first 200 metres.
She gradually wound it up until on the last lap there was only her and Stephie Pennycook in contention.
Mari had beaten Stephie to the silver medal at the BUCS championships last month in a race won by Jess Judd.
But despite hitting the last 400m hard, the Frisby star couldn’t shake off the Scottish Universities champion who went past in the finishing straight to claim victory.
Both girls were rewarded with personal bests, Mari taking her mark to 4min 23.77secs after a courageous run.