You've said "I'm the aunt" out loud dozens of times.
It clears things up for about a minute.
Then the next stranger asks, and the label still isn't yours alone to hold.
Repeating yourself hasn't fixed it. These five truths go further.
1. The agreement covers the adults, not the child
You and your sister settled it. You're the aunt, and everyone nodded.
That agreement did real work.
It also has a limit. A lawyer's paperwork covered legal parentage, but it never covered what anyone says at Thanksgiving.
Clinic screening didn't cover it either. Donors say it left the long-term questions about titles and boundaries for them to sort out alone.
Then a donor-conceived commenter pushed back on a donor's "I'm the aunt."
Some donor-conceived people, the commenter wrote, "do think of the donor as our mother."
That line lands hard.
You control what you say and what you do. She will control what she feels, someday, in her own time.
You can love her well through both.
2. "I'm the aunt" fixes the moment and leaves the assumption
You've probably said something close to this:
"Some imply that I am a mother or that I have a baby, which makes me quite uncomfortable. I feel it's important to clarify that I am not the mom; I am the aunt."
The words are fine. The trouble is who hears them.
Strangers at the grocery store haven't heard about your family agreement. They see a warm woman and a toddler.
Relatives at parties do the same, especially when they comment on how much she looks like you.
A correction tells the other person they got it wrong. An answer hands them the picture.
So try a sentence you can actually use: "I'm her aunt. Her mom is my sister, and I get a visit every month."
It's short, and it's kind to your sister.
It also works with the child standing right there, because nobody is arguing over her.
3. The label and the biology can both be true
Some days you look at her and think about the genes.
You share roughly 50% with her, not the 25% of a typical aunt. Some donors even wonder whether she got "my good traits and not my bad traits."
That thought doesn't make you a mother. It makes you honest.
The label names your role. The biology names a fact. They sit side by side.
Your role is the monthly visit, the birthday, the holiday, and the person she runs to first.
One donor wrote it this way: "For me, my feelings toward her are those of a loving aunt, not a mother."
Sometimes a strange flash of ownership shows up anyway. Sometimes it's baby fever after a good afternoon with her.
Donors describe it as "too many feelings." It's a common experience, and it's no sign you're doing anything wrong.
Some donors take a couple of weeks of distance to protect the aunt role. If you do, tell your sister why, so she doesn't read it as pulling away.
4. If she says "mother," your face will teach her more than your words
Here's a scene from a donor's family.
At Christmas, the child reached for the donor. Her mom reacted with visible hurt in front of everyone.
The child was reaching for someone warm. The adults heard a verdict.
Kids also name things before the family agrees on the name. One donor's daughter and her donor-conceived cousin got close and said out loud, "I love you, my half-sister."
Nobody had planned for that sentence.
So decide now, with your sister, what happens if your niece says it to you.
Here's one answer: "I love you too. I'm your aunt, and I'm not going anywhere."
It's warm, and it leaves her feelings alone.
Then talk with your sister before the moment comes. Recipients can spend weeks worrying that a donor will want a say in how the child is raised.
Hearing it from you first, calmly, is the reassurance she's hoping for.
5. Thinking harder now is how "aunt" stays true
You might be thinking you've already handled this. You told everyone, and the label is settled.
You told the adults. Your niece hasn't been part of that conversation yet.
She will be. What's left to decide is whether she hears the story early and warmly, or late and sideways.
Donors and commenters warn about the plan to tell a child at 18. It can leave her feeling that "everyone has been keeping a huge secret from you your entire life."
The gentler path is a simple story from the start, told through books and everyday talk. No dramatic reveal.
With that story, "aunt" comes with the truth attached.
You may disagree with your sister's timing. Some donors get told it's "none of your business."
You can ask a question instead: "How do you want her to hear it?"
A letter or video from you, kept safe, covers the day you can't be there to tell it yourself.
One donor wrote about the day her niece arrived: "The joy on my sister and her husband's faces when she was born was priceless."
You gave that. Now you get to help write what comes after.
Say your one sentence at the next grocery store. Then call your sister and ask what she'd like her daughter to hear.