What is important here is to determine what are you looking for, as I mentioned before Ran is without a doubt, gay. Therefore, this series now qualifies as yuri into my eyes. Ran's just acting exactly how someone with lots of confidence acts towards their crush: confessing. If anything, this is one of the most realistic and healthy depictions of a relationship that I've ever seen.
Of course, whether her confession leads to a relationship with Keiko or not is another thing completely (just like in real life).