In Re: Jealousy, Tifa being Jealous of Aerith's connection doesn't mean Cloud loves her. My fiancee is jealous of my rapport with one of my best friends (and feels terrible about feeling jealous), doesn't mean I'm gonna leave the fiancee for the friend.
But Cloud, Aerith, and Tifa are in an established love triangle (as stated in the OG gaming manual).
The reason Tifa isn't jealous of Cloud's continued feelings for Zack is because Zack isn't in the love triangle.
It is specifically stated that Tifa is jealous of Cloud's feelings for Aerith because Aerith is Tifa's "love rival."
Until other people are added to this love triangle, it only takes common sense to know why Tifa is jealous of Cloud's continued feelings for her "love rival" Aerith Gainsborough.
As we all know, the hero is stated to "waver" between both heroines. Tifa is jealous because Cloud continues to "waver" to Aerith, even in death.
Is the friend your wife is jealous of a member of your love triangle?
Is your friend called your wife's "love rival"?
Unless you start to "waver" between your wife & friend, your example is irrelevant.