The ex-wife of Tori Spelling's new husband has told of her heartbreak when she learned Dean McDermott was ending their 13-year marriage to be with the former BEVERLY HILLS, 90210 actress. MARY JO EUSTACE tells US TV show THE INSIDER she was devastated when MCDermott announced he wanted a divorce after returning from filming TV movie MIND OVER MURDER with Spelling in Canada last summer (05). Spelling split with her husband of 14 months, CHARLIE SHANIAN, last September (05) - the same month MCDermott filed for divorce from Eustace. Spelling and MCDermott wed in Fiji on Sunday (07MAY06) - nearly five months after their Christmas (DEC05) engagement. Eustace, who is writing a book about her marriage split, recalls, "I funnily enough said, 'Have you met someone?' He said, 'Yes.' I said, 'Is it Tori Spelling?' He said, 'Yes.' I said, 'Have you slept with her?' He said, 'Yes, we're soulmates. She loves me unconditionally.' "I laughed at first. I really thought it was a joke. It was a complete and utter shock. "He made it very clear that they were going to be together. I didn't know whether it was real or not." Canadian TV star Eustace and MCDermott have two children together - their biological son JACK, seven, and a recently adopted daughter LOLA, 10 months. Eustace admits she has met Spelling for the sake of her son: "If she is going to be married to my ex-husband, the best case scenario is that she is a wonderful stepmother and that my son is treated well. That's really the important thing."