Thanks to DarkUFO reader Spike440 for the following info which seems to indicate that she could be appearing in Episode 5.07 and 5.08 as per our filming analysis here.
I heard an interview with the actress (Fionnula Flanagan) who plays Mrs. Hawking on Ireland's RTE Radio 1 last weekend where she said that she would be traveling to Hawaii to film two episodes.
She was being interviewed about the US election and mentions Lost near the end of the interview. The podcast is available here.
Source: RTE Radio 1