The star plays newly promoted Sergeant Georgie Lane in the BBC drama.
Michelle said: "So Georgie is back and training a new batch of medics. There’s an underlying sense of grief for Elvis that we'll see earlier in the series.
"Last season ended on a cliff-hanger and the thing is you don’t know who survives, it’s down the line, she's got a promotion...
"They get back to Afghan and she's conflicted about whether to go or not."
At the end of the last series, Georgie and the rest of 2 Section were being hunted down by armed gunmen before coming to the edge of a cliff.
Moments before the series ended, Captain James ordered them all to jump or risk being shot – and that's where it ended.
But Captain James - who Georgie enjoyed a romance with is not in the new series.
"Unfortunately he’s not back this season," Michelle explained.
"I think with Georgie she's married to her job in a sense she puts her job first. She’s trying to get over the death of Elvis and she needs closure with that."
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Fans of Luke Pasqualino, who played Elvis, will be happy to know he's back this series, appearing in a series of flashbacks that Georgie has.
At the press launch of the show, the creator of Our Girl, Tony Grounds explained: "Georgie is still missing the love of her life.
"She hasn't come to terms with this – whether you'd call it PTSD, or just a sort of deep sadness that she's got."
He also revealed that they had no choice but to kill off Elvis.
Tony said: "We could have sent [Elvis] to prison or on holiday or just not seen him for five years but that seemed a bit daft.
"So we thought let's take this brave way – and he dies on the battlefield in Georgie Lane's arms.
"We were forced into that way of thinking because I love him and I would happily have had Elvis in forever."
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