learning disability?

my 14 year old daughter concerns me in that she doesnt seem to understand alot of simple commands, such as being told to come home for dinner then I would run her to her friends. This was said clearly three times but instead she disappeared on the train and called me from her destination, then got very upset and couldn't understand why I was angry with her.Because of this I missed a PTA meeting.

I very much struggle to converse with her as she seems to struggle getting her point across or telling a story (she'll take a full 5 minutes to tell us something that should take a minute.) She doesnt seem to understand a lot of what is said to her and I start to get frustrated.

She needs to stick to the same pattern eg. bedtime routine and can't "think outside the box."

Do these things sound like a learning disability or like normal behaviour? She seems to do ok at school but struggles to get anywhere near the results at her teachers thought she would get at her 3rd year exams. I dont know if shes being defiant (seems good natured) or just has problems.