Do I say something?

[Tatiannatomasina]

A colleague at work confided in me that her partner does not want a lodger moving in with them. She needs the money (its her house) and the lodger is due to move in at the end of January. The lodger is also our work collegue and has no idea her partner feels this way. I told her she needed to tell the lodger how her partner feels. She disagrees and I know she wont tell him. Should I tell him? If it goes belly up and he finds out I knew I think he would be upset with me.

You don’t need to involve yourself in this, it’s none of your business

I'm not sure why you would involve yourself in this?

MYOB

Surely if it goes belly up your colleague is far more likely to

a) have his hands full finding new accommodation and moving out
b) be upset with his landlady and her partner?

You’re not planning on discussing the fact that you know with anyone, are you? It’s highly unlikely that the landlady would either.

Keep out.
Find another drama of your own to involve yourself in.

One million % keep out of it!

Her house, her bills, her decision.

I told her she needed to tell the lodger how her partner feels. She disagrees

You've done your bit right there.
And you know she disagrees.

So stay out of it now.

Bloody hell it's definitely none of your business. The lodger doesn't have a right to know about private disagreements between this couple. There's no reason to believe that the partner won't be civil with this guy and if you tell the lodger you're going to make the situation awkward.