When someone asks to move in after a week of knowing each other, that’s about as red as red flags can get.

A woman with a close but complicated family history watched her younger sibling fall way too fast for someone she’d just met. So when he asked to move in after a single night together, she didn’t see a single problem with it.

Meanwhile, this older sibling’s danger signals were going off like crazy.

But when she raised her valid concern, she was accused of ruining her sister’s happiness.

You’ll want to keep reading for this one.

AITA for telling my sister it’s a massive red flag that a guy she met a week ago asked to move in with her?

I (26F) have a younger sister, “M” (25F).

We had a really rough upbringing. We lost our stepdad two years ago, our mother is estranged, and we don’t speak to the rest of our extended family.

She feels like her and her sister pretty much only have each other, so when her younger sister started dating, things got a little messy.

Because it’s basically just been the two of us navigating life, we are very close, but I definitely tend to feel protective of her.

M has been on the dating apps recently.

About a week ago, she started talking to a guy who works at her local coffee shop. They have only been talking for a single week.

Things started to move a bit fast for the older sister’s comfort.

Last night, he spent the night at her house for the first time.

Today, he asked her if he could move in with her.

When she told me this, I immediately told her it was a terrible idea.

She tries to reason with her younger sister, but instead of being appreciative, M got upset.

I pointed out that he basically doesn’t even know her, it’s a massive red flag to try and move into someone’s place after one week and one night, and that she needs to slow way down.

M got really upset with me.

M starts to assume the worst of her and her intentions.

She thinks I’m being unsupportive, judgmental, and an AH for raining on her parade instead of being happy that she found someone who likes her that much.

Given our background, I’m terrified of her getting taken advantage of or trapped in a bad situation with a stranger.

But she is so mad at me right now that I’m starting to wonder if I handled it wrong or overstepped.

AITA?

She’s not wrong for wanting her little sister to be safe.

Did Redditors agree?

Boundaries are important, even when you’re head over heels for someone.

This guy is definitely planning something — and it’s definitely nothing good.

This user worries M lacks basic emotional literacy.

This isn’t the behavior of someone who’s well adjusted.

Being the older sibling means being the first one to recognize a pattern your younger sister hasn’t seen enough of life to spot yet, and that’s not a character flaw; it’s just the math of experience.

A man asking to move in after one week isn’t a declaration of love; it’s a manipulation tactic, whether he knows it or not.

Wanting to protect her sister isn’t “judgmental” at all. Loving someone means telling the truth, even when it’s difficult, and looking out for danger signs in the other person’s blind spots.

If her younger sibling needs to let this relationship run its course, then fine, but she can’t say she wasn’t warned.

If you enjoyed this post, check out this story about a woman who was in love with her dream house – and then spring came and her neighbor’s trees caused her to question the purchase.