1) Her plan at Pieta
Even monkey could come up with the idea if it had youki suppressant pills. The idea alone was nothing impressive, getting hands on suppressant pills was. Unless Rubel did all the work for Miria and told her what to do in order to survive. After all it was in his best interest if he wanted the org to have problems with her. That in fact seems to be the most likely conclusion since she somehow knew that by taking half a pill unconscious Claymore becomes cloaked and it's not something Miria could discover by herself.
Miria's plan working was an ass-pull by Yagi since for it to work Claymores had to be injured in a way they would lose consciousness and not die in the process. Also, Clare was the only one of the bunch that could survive Pieta (although in her case it could mean becoming an awakened being) by her power alone. How could all 6 of them (Yuma was already out) be hit just like that when they were surrounded from all sides O_O ? That's like all of them would hit a jackpot in a lottery with chances 1:14 000 000. ABs, being on all sides would see the hit in every possible angle and no one would notice it? 6 times?
And Miria didn't think about such an obvious alternative and much more efficient strategy as escaping using the pills. Instead of handing over the pills, explaining the situation and making everyone scatter she preferred to go with her plan which resulted in only 7 Claymores standing. Miria, while having huge amounts of pills (they had them even after 7 years and fed them to Audrey and the rest) decided to fight instead of making everyone scatter while being cloaked. They had time to escape but didn't. I could understand it if she didn't know Organization's true colors but she had no reason to obey them in that situation. I highly doubt that there would be more casualties if she did that. In fact she might have been able to crush the organization without lifting a finger. Male ABs would have no reason to pursue Pieta warriors, they were heading to the Org. But Miria did exactly what MiB wanted anyway. Hence she's a retard.
2) Her plan to defeat Hysteria
That's basic "divide and conquer" strategy. Haven't you heard about expression "two dogs fight for a bone and a third runs away with it" or "when two quarrel, a third wins"? And it only worked because Yagi made a total idiot out of Hysteria and Miria super lucky. I mean, how come Miria wasn't hit by any of the numerous attacks? She basically went into a shredder without being hit by the blades even though her opponent was. That's absurd. In other words it was not because Miira's plan was genius. Dumbing someone down is easy, making a genius out of him is not.
3) Her plan to use Raki to bring back Clare
Again, nothing even remotely brilliant in this. On the contrary. Fab 7 (+Galatea) were near the blob earlier and haven't triggered any reaction and Raki was the only other living person who knew Clare so taking him along wouldn't hurt. But to be honest, earlier they didn't even try to do much about her AFAWK since they were afraid that would free Priscilla and Destroyer along the way. Which brings us to: Miria is a retard. Her plan was to let Priscilla and Destroyer escape to not let Cassandra power up Priscilla. So instead of fighting Cassandra she thought it would be better to fight not only her but Priscilla and Destroyer too O_O. And didn't think that after freeing her, Priscilla could go to Cassandra to power-up anyway, lol. What Miria did was many times more risky and had no logic in it. And in the first place, where did she get the ridiculous idea of Cassandra powering Priscilla up from? That doesn't make any sense and has no explanation besides that Yagi has decided to let her know that.
And thinking that Raki, who Clare has known for a few months at most would have bigger influence than friends she knew for over 7 years was ridiculous. Not to mention that present Raki doesn't even remotely resemble the Raki she knew (not his voice, nor his appearance).
If you ask me, Miria had only fail moments. Her every "genius" plan was stupid and/or extremely risky and worked only because Yagi made it so. Logic had nothing to do with it. Other example is how she has convinced everyone to follow her. In chapter 123 on the other hand, Miria looked like a retard when she asked Deneve again and again "Huh?" after our favourite Yagi's mouthpiece explained things to her. And here's another example. There is many more but I'll stop at that for now.