World of Darkness – Can a Victim of Diablerie's Soul be Held Back in the Diablerist?

My last campaign has reached a rather tragic point, marked by Diablerie, which happens more often than it should.

The blood-tied woman of a character who diabolizes the child of this character had fallen prey to the child's diabolism process and continued to sleep with the child's lover.

After this character got wind, the experienced Diablerist decided to put an end to the inhabitants of his wife's body. Well, since he liked his wife, who supposedly still lives in her own body, he wondered what she could do.

If someone is diablerized, can they "stay alive" in him through the effort and "grace" of the diablerist?

She is a higher generation than he (7th to 8th). V20.