Jessica's place is incredibly beautiful and she was responsive and helpful. Full marks :)
Ano Syros is up a steep hill from the port town, and is a stunning old village with traditional narrow streets and views over the sea. There are a handful of shops, bars and restaurants in the town itself, which come alive in the evening. We would particularly recommend cocktails at Theosis; some of the best we have ever tried, at a reasonable price and super charming street seating, and Souvlaki at "Χύμα και τσουβαλάτα"; no frills, but seriously tasty.
Jessica's place is on the 'main street' (still only about 2m wide!), and just a few feet from the best spots. The space is exactly as described.
We came in high season when car hire was expensive, so tried to make do without. This worked okay for a couple of days, but I would recommend getting a car if staying for longer. The taxi's are cheap (5-10€ to the port), but are not easy to order (ask a local to order for you, as they seem to have more success!) there is a free bus that goes to the port a few times a day and another cheap one that circumnavigates the island.
Overall a wonderful spot that I would highly recommend for your trip to Syros!