AITA for jokingly calling my daughter's best friend our fake adopted kid in front of her parents?

UPDATE: starting off, this whole thing got blown out of proportion because of my anxiety. I was hoping to hear from people who have actually experienced this situation on one side or the other.

I spoke with BFFs mom today. It had nothing to do with my comment about BFF as our adopted daughter. She was actually very happy to know how much we care about her daughter.

It was exactly what my daughter said it was; Mom and BFF had an argument earlier that had nothing to do with my family.

To straighten things out; BFF is not always over at our house. She has several different friends she spends time with, but she spends a lot of time here. There is no keeping score on who has come over, who has paid for dinner, or entertainment. Our house is the "cool house" with the kids friends over a lot (not ever day

Also, I have taken her with me to a restaurant maybe twice. Family style, casual, nothing fancy, or with reservations.

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My daughter (12yoF) and her best friend (12yoF) have been BFFs since 1st grade, consequently the BFF is over at our house quite often. She is over at our house much more than having my daughter visit because my daughter has OCD and doesn't like to leave the house very often.

Last weekend BFF came to our house after school, and later in the afternoon called her parents for permission to sleep over. Parents said yes, we needed to stop by BFF's to get her stuff. My husband and I had planned to go out to dinner before the BFF1 spending the night had been brought up. Neither my daughter or son (12yoM) wanted to join us.

Normally, this is not a problem just going without daughter and son, but we couldn't leave BFF at our house without supervision. I'm pretty sure her parents would not be cool with that. We discussed the situation at home and decided to take BFF with us to get her things and then to dinner as we needed to feed her either way.

As we stopped at BFF's house to get her things, I jokingly mentioned while chatting with BFF's parents that BFF was like our fake adopted kid, or something like that. We continued talking, I mentioned that BFF is a great kid, doesn't swear, is respectful, etc. BFF finishes grabbing her stuff and gives her parents kisses an hugs goodbye.

On our way to the restaurant BFF gets a call from her mom to come back home, there was something mentioned about her mom's sister getting out of the hospital, but BFF later tells me that that wasn't the problem. We promptly bring BFF home. BFF cried a little on the way home. Later I texted mom to ask if everything is ok, and offering help if any is needed.

Days later I asked BFF (while she was at our house) if everything was ok with her aunt. She tells me that the aunt being in the hospital wasn't an issue. The problem was the remark I had made about her being our fake adopted kid.

I feel so bad that what I said made them that uncomfortable. I have had other friends parents say the same thing jokingly about both of my kids.

BFF tells me now that her mom wants to talk to me about it, or both BFF's parents want to speak with me and my husband; it's a little unclear but I chalk that up to BFF being 12.

I'm not sure of exactly what to say, except for apologizing and making it clear that what I said was not meant to be taken as anything other than a joke. I am worried that I might have ruined my daughter's relationship by being a completely clueless ahole.

AITAH for jokingly saying daughter's BFF was like our fake adopted kid?