Helia's place is extremely well located. Only five minutes walk from the Martim Moniz metro and close to all the areas you would want to visit in Lisboa. The place is a semi-basement so there is not much light as an FYI but all the basic things you would need for a short stay are there. The price is reasonable for the location and the amenities you get in comparison to the other options around.
Accessibility wise: Lisboa has many hills and stairs and the way to Helia's place is climbing up many flights of stairs and going uphill from the metro as an FYI if you decide to walk it with your baggage like I did. If this is too much I would suggest getting a car to her place instead!