When someone doesn't do as they say they will do, do you just assume they forgot or have good reason?

For instance I have very positive signs that my babies mother wants to get back together. Like... sending me a bunch of zodiac sign stuff that talks about how our months are great together and then her asking if that sounds like us then a little winky face. Then later in the night sending me texts talking about her playing with herself...

OK back to the question. So she said she would call today about our date tomorrow and get shit worked out because there are some logistical things to work out. She never called. So I am assuming she forgot she said that or just assumed that we are still on for our date and didn't think she needed to call or some other random shit.

So when someone says they are going to call you but never do... do you assume they had good reason and just be confident in the fact that there is no problems?