To have given this as a gift?

If my DH was slagging my mum off on social media I'd be gutted regardless of who he was friends with. And you were friends with her daughter, clearly.

A private text chain is one thing, social media is something very different and in no way a "safe space" for slagging family members off.

But the whole helping me out thing was so last minute. And because my last day at that particular workplace is on Thursday, I may well never see her again.
I honestly did mean well.

If my DH was slagging my mum off on social media I'd be gutted regardless of who he was friends with. And you were friends with her daughter, clearly.

A private text chain is one thing, social media is something very different and in no way a "safe space" for slagging family members off.

Gosh there are some ungrateful types here. What happened to "it's the thought that counts"? Even if I didn't like Limoncello or thought maybe someone had tried it, OP, I'd still think it was a sweet, generous thought of yours.

No 😂
She can barely work a mobile phone!
I also don't have a lot of DH's family on Facebook so its a safe space for me. MIL has a lot of issues, mainly because her family have allowed her to say and do whatever she wants without question as "that's just the way she is". I however, am not so cool with letting things slide and even my dh now agrees that things should have been pulled up in the past so she wouldn't be as blunt as a brick as she is now. I just found it more ironic his sister said "you can't say that!" but actively ignores her mum for months on end because she's so hard to deal with. It was just a shock for her that someone verbalised it. I have since seen sil and she is absolutely fine with me, she's as daft as a brush and has forgotten she even has me blocked. It doesn't bother me in the slightest. I just find the whole thing comical. But seriously don't open a gift, eat half of it and still gift it. It's not cricket.

No 😂
She can barely work a mobile phone!
I also don't have a lot of DH's family on Facebook so its a safe space for me. MIL has a lot of issues, mainly because her family have allowed her to say and do whatever she wants without question as "that's just the way she is". I however, am not so cool with letting things slide and even my dh now agrees that things should have been pulled up in the past so she wouldn't be as blunt as a brick as she is now. I just found it more ironic his sister said "you can't say that!" but actively ignores her mum for months on end because she's so hard to deal with. It was just a shock for her that someone verbalised it. I have since seen sil and she is absolutely fine with me, she's as daft as a brush and has forgotten she even has me blocked. It doesn't bother me in the slightest. I just find the whole thing comical. But seriously don't open a gift, eat half of it and still gift it. It's not cricket.

Gosh there are some ungrateful types here. What happened to "it's the thought that counts"? Even if I didn't like Limoncello or thought maybe someone had tried it, OP, I'd still think it was a sweet, generous thought of yours.

Is your mil on FB?

I think you'll feel better if you do this. Just say you hadn't noticed when you gave it her but then someone in your household said they had already opened it, then give her new gift. You'll both laugh and all will be well. She'll know you're a thoughtful person.

I didn't slag her off, more just in a jokey what's she like kind of way.
I'd say actively giving someone a half-eaten gift (and not accidentally mind, but in a "I fancied some of that so I took it" way) is worse than a comical bewildered facebook status. It's akin to dishing a guests dinner up and having mouthfulls of their food to try it first before handing them the plate!

WTF

you posted on FB about your MIL eating your chocolate? Ok she was wrong to do that, but come on. That’s not on.

Just text her and explain the situation. Just say you thought she might have liked it but your dd has since informed you that she did pour a tiny bit from the bottle to taste. Because of this, please feel free to tip it away and you will get her another gift. From the sounds of things she will probably tell you not to be silly and not to waste your money.
Last year my mil bought us easter eggs. She bought one for each of the kids, one for me but nothing for her son (DH). Anyway, she opened mine first, ate both bags of minstrels that came with the egg and still gave it to me and saw nothing wrong with this. I posted about it on facebook and what a numpty she could be at times and my sil blocked me lol. Ah families.
I think there's a difference between gifting someone something you've swigged (or eaten) half of, and a bottle that may not even look like it had been opened anyway.

Send her a message:
When I told my family I'd given you that bottle, one of my teens 'fessed up to having had a taster from it. I'm so embarrassed, and I'm obviously going to have to start locking the drinks cupboard... I hope you can enjoy the rest of it, and I've told the teen that they owe you a drink!