Hilchos Lashon Hara chapter 8, section 10

Now we will explain in front of whom it is forbidden to speak lashon hara.

The prohibition is the same whether he tells it to other people, to relatives or non-relatives, or to his wife. The only exception is something he needs to tell her because of a benefit it will bring in the future. For example, she sells on credit in their store to bad people, and it will be hard to collect the money from them later. So he tells her about their bad character and warns her not to sell to them.

In the same way, a partner may tell his partner about people he thinks are not trustworthy.

Even if he does not know their bad character himself, but only heard it from others, he may also tell her what he heard about them and warn her about them. But it is forbidden to believe what he heard about them; he may only be cautious.