My husband is dating my niece

Dear Ladun,

My niece stays with me. I have been responsible for her
education and her up keep before I got married to my husband. So when I got
married she moved in with me. She passed out of secondary school last year and
still at home waiting for her admission. Her closeness with my husband is
something I don’t understand. She is freer with him than me. Something tells me
they are about to start an affair. This faithful night I called my husband and
asked him what was going on between them, he said nothing. I told him to
remember that this girl is my niece, my blood and he should be very careful. He
fought me over it and I saw more signs.

I told my grandma and my aunty (her own mom) they said I was
lying that I should give them a better reason if I want her out of my house. I
feel like sending her out right now but I don’t have a genuine reason yet. I am
not a kid, I know when something is about to happen. I can read through their
body language. I sometimes hear her discuss with my husband in the living room
and when I move closer she stops. I hear her voice clearly and when my husband
leaves for the office I do call her and ask what they were discussing. 

This
girl will start swearing that she didn’t outer a word to my husband not to talk
of discussing anything with him. I need to catch them this week. More so, her
education is finished because I am no longer interested in spending a dime on
her anymore. Imagine hearing your niece voice and she still has the effrontery
to swear that it wasn’t her voice I heard. I am totally mad right now and want
this girl out immediately. Who knows how I can catch them?