I think the whole situation raises a few curly questions - like why on earth is she using you for a reference, when you effectively sacked her? Does she not realise she did a crummy job? Does she think that you don't know she did a crummy job? And who uses someone (particularly someone who sacked them) as a reference without even checking first??

A bit concerning, frankly. It really doesn't strike me that she has matured or wisened up much, TBH.

I would be honest, and courteous balancing the different issues at play.

If you wanted to be delicate, you could say something right at the start like, "I'm rather surprised Betty is using me as a reference." That way you're making a pretty obvious point without actually slamming her.

For the meat, you could be clear without being too negative by saying something like, "it didn't work out and I had to let her go, because at the end of the day my kids needed more supervision than Betty could give."

If they want more details, you could just say something like, "sorry I can't be more help, but I'm not comfortable going into more details. I have tried hard to leave things on good terms, as Betty is a family friend and a nice girl." or whatever.

I think that gives enough of a picture without being negative, and without getting into any details.

IMHO references need to be frank and honest (and probably confidential) because anything else isn't fair to the potential employee or to the employer. But maybe Nai or someone can give some clarity as to whether you can't say anything negative ... I've certainly never heard that.

But when one particular person asked if I would be their character reference, I told them outright not to ask me, as they wouldn't like what I had to say. My stance in life is that I won't lie to you and I won't lie for you ... and I appreciate the same in return.