User blog comment:IamJakuhoRaikoben/Chapter 381: Where Demons Live, Review./@comment-74.61.219.92-20140420031503/@comment-7418318-20140420085844

Yes dear Anon, you are absolutely right. If something does not work on the first attempt, it is the logical and right thing to do to just give up. Because failing once is irrefutable proof that it is absolutely impossible to accomplish.

Apart from what Rai already explained, the first time Mirajane tried to fully take Sayla over without even putting all her effort into it. When that did not work, Mira tried something else, that's probably easier to achieve than a full Take-Over and put all her effort into it on top.

Which all sounds very reasonable and logical to me.