Constable Joanna Parrish
Jo arrived in Mt Thomas in the episode 'Hello Goodbye', screened in mid 1999.  She caused a bit of trouble when she first arrived but has settled in well.  In the early days, Jack had his eye on her, but Jo was still recovering from a recent split from her psychotic boyfriend.  Despite having not been in Mt Thomas for too long, Jo is stunned by the death of Maggie Doyle.
When Tess turns up, it seems that they will never get along. As they can't see eye to eye on anything, whether it is the outcome of a case or what Jo calls her while out on a job (she doesn't like being called Tess in front of "customers") it really doesn't look like they will.  Jo finds Tess bossy, irritating, frustrating and non-compassionate.  She believes that all coppers should be fair and to her, Tess is too preoccupied with moving quickly up the ranks rather than listening to other peoples ideas - even those of her colleagues'.  Even though Jo wasn't there too long, she found a friend in Maggie and she firmly believes Tess is a less than fantastic replacement for her.
Jo never knew about Tess and Jack's relationship, but she was upset when Jack left.There obviously is light at the end of the tunnel though, as the arrival of the new cop Jonesy seems to have created a new love triangle in the station - Tess, Jo and Jonesy. 
Jo Parrish
Jo thinks Jonesy is the best thing since sliced bread, but Jonesy hasn't noticed her because he quite likes the look of Tess.  However, Tess is very wary of being burned again and is still getting over Jack to see Jonesy's interest in her.
Jo has a few skirmishes relationship-wise in Season 9, but the biggest would have to be a one-night stand with her colleague Snr Detective PJ Hasham.  She moves in with PJ and Ben and one thing leads to another, leaving the pair extremely uncomfortable the following morning.  A hostage situation brings them back together.
A shooting in the episode Teamwork has Jo undergoing councelling. PJ refuses to belive that she is not affected, and once again they find themselves in bed. In the last ep of season 9, Jo tells PJ that she loves him, but is heartbroken when he doesn't return her feelings.