emails from 1 specific person do not arrive


New Email

I subscribed to hotmail about 2 weeks ago. In general I'm pleased with the services hotmail provides. However, I have one particular problem. The emails from 1 person do not arrive in my inbox. If I send emails to that person she gets them, but if she sends something back, I don't receive it. From other people (as far as I know) I receive the emails, but only from that one specific person I do not receive the emails although they are in her 'send' file.
How is this possible? I really don't get it.
Thanks for you help.