If a co worker said..

[MalevolentPrawn]

"You can tell how hard she is trying" (in the context of doing your job) is that a compliment or an insult?

Insult.

Insult

It would depend on the personality of the colleague, the context and the tone of voice tbh.

Hmmm, it’s patronising really isn’t it? I don’t think I’d take that as a compliment.

The colleague is genuinely nice, and kind. It came after saying how nice I am, apparently.

It depends on context.

The colleague thinks you are being nice, that you are trying hard to be nice and is trying to compliment the effort?

It sounds to me like someone telling you that despite trying hard you're not doing well enough.

That was my worry, Disfordarkchocolate

Then I'd take it as a statement of fact. She can tell how hard you're trying. And she thinks you're nice.

Don't go looking for offence, upset and insults round every corner. More often than not people mean well, or at least neutral.

........backhanded compliment.

It depends on context.

Ask her, if she's nice she will be truthful and perhaps support you to do better.

Completely depends on context. Could be that you can tell how hard you're trying because you always give everything your all and that's been recognised.