It can be really devastating when people you love let you down in the most unexpected ways.

This girl was happy to help her sister out, but after finding out she’d had an affair with a married man, isn’t sure she likes – or trusts – her anymore.

Check out the full story.

AITA for Telling My Sister I Don’t Know if I Love Her After Finding Out About Her 5-Year Affair?

My sister (32) moved in with me because she got pregnant 5 months ago from what she claimed was a “one-night stand.”

I love my sister, so of course, I took her in.

She was very welcoming towards her sister…

My husband is overseas for 6 more months, so it was nice to have her around because I care about her very much.

On Monday, I came home and saw my sister and a strange woman in a screaming match on my doorstep.

I obviously didn’t know what was happening, but I saw the woman poking my pregnant sister’s shoulder, so I intervened.

Things got really bad!

I sent my sister inside, and she begged me to send the woman away.

I didn’t understand what was going on, but I wanted the altercation to end for everyone’s sake, so I told the woman as much.

Then she started screaming, asking me if I was also sleeping with her husband.

I was like ?????

And then she basically revealed that my sister had been having an affair with her husband for 5 YEARS.

FIVE YEARS!

That was so UNEXPECTED!

She had everything printed out—chats, photos, emails, receipts. It was disturbing to see, and I didn’t want to go through it all.

But a few things were established:

My sister knew about his wife.

She knew she was the mistress and liked it.

This woman was a stay-at-home mom to their four kids, one of whom has a severe disability from a car accident.

She found out a lot more than she wanted…

Her husband knew about my sister’s pregnancy and even took her on a babymoon to celebrate it.

The affair had been going on the entire time, with my sister believing he would eventually leave his wife for her.

My sister had fully embraced the role of being “the other woman” and was emotionally invested in their relationship, despite his repeated lies about leaving his wife.

I told the woman I was very sorry and that I obviously didn’t know, but I asked her to leave because this wasn’t going anywhere, and I didn’t want the neighbors to call the police.

The lady wasn’t letting it go…

She was furious but gave me her number on a post-it, begging me not to let her husband stay at my house.

I assured her that no man was stepping foot in my home.

My sister was begging me not to believe the woman, calling her a vindictive ex-wife.

I told her, “Alright then, let’s look up the marriage online. Let’s see if a motion for dissolution of marriage was ever submitted.”

We fought hard.

My sister kept saying I would never understand and that they loved each other, but he just couldn’t leave his wife, blah blah blah.

I called her dumb and naïve.

They broke into a fight afterwards…

The next day, I told her she could stay here because I didn’t want her to become a financial burden on that woman in any way, but I also told her that, right now, I didn’t want to engage with her.

My sister asked me if I still loved her, and I told her honestly, “Right now, I can’t say I do. I will always help my nephew and not endanger you, but I can’t like you because you’ve shown me you’re not a trustworthy person.”

Things got really distant…

I told her I didn’t trust her not to try anything with my husband, and I didn’t trust her with anything at all, so I made her sign a tenant’s agreement.

She’s been begging me to forgive her, and I told her there’s nothing to forgive.

I just don’t know who she is anymore.

AITAH

Geez! That must have been nerve wrecking for this girl!

Let’s find out what the Reddit community thinks about this girl’s reaction.

That’s right! This user thinks the sister is very problematic for never bringing this up.

This user blames the sister and the cheating husband!

Exactly! This user suggests kicking the sister out of the house before it is too late.

This user hopes that this situation knocks some sense into the sister.

This user knows that this girl is right for being upset about everything.

Why can’t the sister simply admit her mistake?

That’s such a hard thing to do for some people.

If you thought that was an interesting story, check out what happened when a family gave their in-laws a free place to stay in exchange for babysitting, but things changed when they don’t hold up their end of the bargain.