It's not that my Shep feels threatened by Dr. Michel. She knows Garrus wouldn't be interested even if he was less oblivious. But... she does have a short temper when it comes to flirting (with her or her boyfriend), so if it turns out that Dr. Michel really is hitting on Garrus after knowing that the two of them are in a relationship, she'll be angry. xD
Kiara Shepard: Just stay away from my man. >_> Do you know how long it took me to make this guy realize that I was interested in him? Two years! You want to date Turian Batman? Get your own.
Garrus: I... what? Two years? ...Turian Batman?
Tali: *is very amused by this, and eating the chocolates*
Reporter: Oooooh, a scandal! I must tape this.

Commander Shepard, how do you feel about--?
Kiara: I will
not talk to the press! *Renegade interrupt punch!*
Dr. Michel: O_O *backs away*
Garrus: *turns to the crowd* Yeah, that's my girlfriend.

The crazy one.