In her research project, ella wants to study the processes involved in lesbian partners adopting children. she starts off by interviewing lesbian couples who have adopted in the past, and they in turn, give her names of other lesbian couples who have adopted. the process by which ella gets her sample is called

Snowball sampling

Explanation:

Snowball sampling -

It is the sampling method , in which , the presently existing study are recruited further for future subject , is known as snowball sampling .

And the sample group increases in a way a snow ball increases while rolling .

Hence , from the question ,

The correct term according to the given question is snowball sampling .