If you paid through June 30, but she terminated June 20, she owes you at least that ten days of rent. (She may also owe you the other days between the fire and the termination, if the apartment was not usable.)

Whether she pays or not is a different question. If you’ve tried to discuss it, but she declines to offer a solution, you could try sending her a 93A demand letter setting out exactly what the problem is and what you’re looking for as a resolution.

https://www.mass.gov/consumer-protection-with-the-courts