Originally Posted by Claudius
Again, I love the Andrea character right now. Another character who's experienced a tremendous amount of growth and you can see a lot of internal conflict with her. Again, early on in the season where she mentions to Michonne to leave her alone and essentially allow her to die. While in the compound, she again chooses life and her facial reactions to the news of how you turn when you die were/was quite interesting.
She has no reason to mistrust Merle or the Governor at the moment. She's worked with Merle before and I don't believe he ever threatened her beyond the confrontation on the roof top. He was for hostile to T-Dog for racial reasons. When the world around you has crumbled, it makes sense to latch onto anything or anyone familiar. He's familiar and if he's survived, it provides you with a sense of hope that you too may be able to survive.
As for the military guys, makes sense. A single man approaches, you're heavily armed he's not. Why would you have your arms up? Ambushes happen all the time (in real life against heavily armed military units). It's not that unforeseen or unrealistic.
In the one episode of the show where we saw both characters together it showed who Merle really was (a racist, violent brute), giving all of the reason to mistrust him? That's a bit of a wild conclusion you're making imo. If anything, it just reinforces the idea that Andrea is naiive and keeps making huge mistakes, just like she did with Shane. If there's anyone she should trust, it's Michonne, who saved her life and kept her alive for 7 months, and at this point Michone obviously doesn't trust the Governor who is keeping them imprisoned while trying to make them believe their free. All in all, Andrea makes stupid decisions, and has ever since her sister died. She's been facing the same internal conflict since then, and there's been no character growth (ie. repeated stupid decisions - wanting to kill herself, fling with Shane, fighting with Dale, and now trusting a group who has a key contributing member that is an obvious villain)