Most Helpful Girl
She is probably just sleep-deprived.
MOST teenagers are sleep-deprived already, since high school starts at an ungodly hour that's totally unsuited to the teenage circadian rhythm.
... Throw in just a *little* extra sleep deprivation, on top of that... and, yeah, those kinds of mistakes aren't uncommon at all.
Most Helpful Guy
Well those examples don't show that she's necessarily dumb or bad at logic, but I have seen some other people who are truly bad in those areas, and it can be exhausting.
When you're in a relationship, you have to be like a team, especially when it gets serious. You have to plan and make decisions together, etc. And if she is not very bright, you will end up having to do a lot of the work yourself and carry her, which is never a good thing. And you will have to remedy a lot of the mistakes that she makes. Basically, there is a lot more work for you, haha.
There are really no pros to being with a dumb person in the long run. Some people make the mistake of thinking that a dumb person is more likely to be nice and kind, but that's not necessarily the case. Kindness and smarts are not related.