Con ella se han ensañado

[poli]

I use Spanish every day but sometimes simple sentences confuse me.
Does this mean they have taught her a lesson?

[Rusty]

The last word should be enseñado, I suppose.

More context is needed, but this is what I think it could mean.
The reflexive construct is most likely the passive voice - it has been taught. It really doesn't matter if ha or han is used, both are translated the same. The con ella prepositional phrase could be either with her (a person) or with it (a feminine object).
I would think it is the latter case in your sentence. If I were talking about something feminine that was instrumental in teaching someone something, I could use this sentence:
With that (some feminine thing) it has been taught.

[poli]

I must have been half asleep when I posted my question, because now I understand it. What was written is "con ella se han ensañado."(they have
angered her).

[Rusty]

Oh, OK, in that case, your translation is correct, but I understand the verb to be stronger, as in:
They've infuriated|irritated her.

The verb has the sense of infuriating someone (who can't necessarily defend themselves) and getting some satisfaction doing so.

[CrOtALiTo]

I have an opinion about it.

Poli. you have set in your title.
Con ella se han ensañado

I think that the best way to translate that oration is Como ella misma se ha enseñado, or you can to use this Con ella se han enseñando los demas.

I feel that your sentence the fault some of sence in itself built, but anyway this is my own view point.

[Vikingo]

Hmmmm, I have another suggestion:

They have gotten angry with her. That is, something she said or did made them angry. Could this be the case?

Saludos

PD: now that I look more closely in the dictionaries, I might be the case that they have indeed mistreated her, or shown her no mercy, taught her a lesson etc. From Oxford: "se ensañaron con los prisioneros: they treated the prisoners mercilessly".

[poli]

Escrito originalmente por Vikingo

Hmmmm, I have another suggestion:

They have gotten angry with her. That is, something she said or did made them angry. Could this be the case?

Saludos

PD: now that I look more closely in the dictionaries, I might be the case that they have indeed mistreated her, or shown her no mercy, taught her a lesson etc. From Oxford: "se ensañaron con los prisioneros: they treated the prisoners mercilessly".

Wow. That's impressive research in your PD. I think you hit it on the nail

[Tomisimo]

Building on everyone else's research, how about:

Con ella se han ensañado.
They delighted in tormenting her.

[poli]

Tomísimo and Viking both have got it right. Tomísimo adds to it indicating
that torurers revel in their profresion.
Sometimes Spanish is like a puzzle ( ) figuring out the roles of the pronouns when they represent the passive rather than the reflexive.What seemed like a simple sentence had me stumped.

[Rusty]

Escrito originalmente por poli

Tomísimo and Viking both have got it right. Tomísimo adds to it indicating that torturers revel in ...

Yeah, that's what I said - "they get some satisfaction doing so."