Perfect location to stay at in Paris. The flat is just a few stops away from Montmartre (my favorite part of the city) and the bonus is that train station is round the corner from the street. Arc de Triomphe is about 25min walk, safe to walk at night. The area itself is very lively but despite of that you won't hear any noise in the apartment even when you keep the windows open.
I couldn't meet Severine and there was a slight problem with the check-in, but she took really good care to resolve the issue. If I were to come back to Paris, I would prefer to stay at Severine's.