Gema is an exceptional host. She is vey nice, responds quickly and does her best to make you comfortable.
Keep it in mind that the room is in the attic, so you need to go on the third floor (and drag your suitcase) thus if you have too many stuff it might be difficult.
I am fishing my memory to find some minuses of my stay, but fail.
A tip: if you are going to explore Boston you will definitely use T - their public transport, Gema’s house is not in a walkable distance to the downtown. The best thing is to get a CharlieTicket for a week/day depending on the duration of your stay. A week pass is around $22. Since a regular CharlieTicket is $2,75 your benefit is evident.