Translation:Sister and Rehema are Tanzanian cooks.
Wapishi (class II) is the plural for mpishi (class I).
From the verb -pika (“cook”).
mpishi (m-wa class, plural wapishi)
1) cook (a person who prepares food for a living)
This class is also known as Class I (in the singular) and Class II (in the plural). It is used to refer to people almost solely; the two notable exceptions are mnyama (“animal”) and mdudu (“insect”), which both serve to categorise animate objects. These prefixes may be added to adjective, noun, or verb stems to express the idea that a person has that characteristic, like Kenya (“Kenya”) → Mkenya (“Kenyan”), or -gonjwa (“sick”) → mgonjwa (“sick person”).
I thought it would be Rehema's sister. In my native language (Chichewa/Chinyanja) "asisi a Rehema..." or "sister wa Rehema..." meaning Rehema's sister, and these languages are quite similar, so i just thought...
So if its the two of them, surely you'd start with the named subject like "Rehema na dada lake..."