I stayed at Karimas house for 2 months. She was there at the same time for a little while too. She was very kind and helpful. Even when she wasn't there, it was always easy to get in touch with her.
The room was big enough for me and it had a lot of storage space. The kitchen was equipped with all basic needs so I could cook some meals.
Many people complain about the area La Chapelle. It's very multi cultural and the vibe is definitely not the stereotypical Parisian atmosphere like from movies. But I never had any trouble in the area. You definitely have to be careful walking alone as a girl at night and be careful about pickpockets in and around the metro station, but that's just like any other district in Paris too.
La Chapelle is easy to get to, especially because it's so close to Gare Du Nord and there are many nice sightings in walking distance, like Montmartre with Sacre Coer, or the canal Saint Martin for example.
Overall I recommend Karimas apartment. It's a good value for the price.