What IS the 'right' way to behave?

I would go up to her and say:

"thank you for returning the [item], I need the other one back now thank you.  I would have told you before but I have barely seen anything of you for some reason."

Sometimes the power is in what's not said.  It will be obvious to an NT what you mean by this.

Have you also considered the possibility that she is just being mean and is not a good friend towards you?

Taking autism out of the equation it sounds to me like she is in the wrong.  Obviously it is hard to tell without knowing the exact interactions between you and your workplace situation etc etc.  But it is generally polite to return borrowed items, and to respond politely to social interactions.  Sometimes NT people do not do this because they are themselves breaking social convention, to avoid embarassement or avoid a conversation where they have to admit not wanting to socialise with someone else, or just because not everyone is a nice person.

In any case, showing your anger and having a rant at her means you would lose the moral high ground (if she is being nasty) or the opportunity to resolve the misunderstanding (if there has been one).

Maybe try having a private rant at her in your head, go somewhere you won't be interrupted and can't be overheard then pretend she is in the room and have your rant - but don't do it to the real person.

Reading your original posting Autist, I sense a number of issues.

Have you made it known to others you helped her? People can be quite precious about receiving help, particularly if it is to do with expected work skills - something she should have been able to do for herself. You say she knew nothing about the ways in which you helped her, but did you makee anyone else aware of this? In any way that would acutely embarass her?

The politics of work places are really tricky and difficult enough for NTs to negotiate, far worse for people on the spectrum who don't get the right feedback.

The second thing is working out where the point of issue lies. You perceive that she has left the EYFS lying around the office and not returned something else you loaned her. Are you sure that the loaned items are the reason for her now ignoring you, or have you considered other factors, including events since you loaned her the items?

Because people on the spectrum don't pick up on all the information that seems to be available to NTs, all you can use to explain things is the fragmentary evidence you have to hand. And you are likely to work through all the permutations you can think of. But there may be information you don't know about.

For example in office environments there's a lot of gossip and some of it is malicious. The reason she is now ignoring you may be for a whole range of reasons, and these could include things you were not party to. So what you must try not to do is get angry (difficult I know). I'm still raging in my head about perceived hurts thirty years ago - I'm never going to get any resolution, and so the stuff keeps coming back to me.

The way people respond to stuff loaned really perplexes me. I don't properly understand it. For example in a conversation someone said they liked a particular type of music and I volunteered that I had some CDs of it. This person asked to borrow them and I loaned them. Months later I ventured to ask for their return, and she got really sharp with me and just said "Don't you dare!". I've never pursued the matter again, and I've never got my CDs back, nor have I been able to buy replacements. It never made any difference to a friendship otherwise, but I've never worked out what happened. I assume she perceived them as a gift rather than a loan.

NTs seem to have a more relaxed way of getting over difficulties. It involves exchanges of information I don't understand.  My own limited perceptions are just my end of a dialogue the other side of which I do not comprehend.

It is not easy advice therefore, as I cannot resolve such situations either. But somehow you've got to try to avoid letting these things get to you. People on the spectrum will feel resentment for years. NTs somehow sort it out, though I do know of situations where NTs get stuck in similar ways, if another party offers no explanation. Byt they are better equipped than people on the spectrum to find resolution.

That would be good.... I am sorry I cannot offer any constructive advice about your friend... May be a short text to her explaining how you feel would help. Hope it all sorts out 

I'm so sorry I shoudlnt have been so horrible. Would it be ok if I make you a post so people can help you mummy51?

@mummy51 have you sorted out posting a new thread with your request?

Autist, you are being harsh.  I know you are under stress but it's unfair taking it out on others for no reason.

 I am sorry... I am new to this sight and thought I was starting a new discussion... I apologise...

Thank you. I am so glad you replied. Ugh. I know it's right. It's not what I feel like doing. It's like I want to metaphorically stab her in the head using words in a text message but I know I can't. thanks.

Hi Autist,

I would send a polite but curt message telling her you needed the things back asap. She is not worth your time if she cannot explain to your face why she has not repied to your messages and been cancelling meetings. Ii know it is hard, but try not to let it bother you. Sending a message like that gives you the upper hand because you have not behaved rudley or irrationally. Dont waste your energy on it. Good luck  xxxxx

fine. don't fucking help me just because I'm not a clueless parent with a three year old.

thank you but that is not very helpful. maybe you could start your own post about this.

Hello,

I wonder if other parents could offer advice / support. my beautiful princess has just started nursery , half a day at school. She is 3and a half.

At school they are great and tell me she is doing well.... At home she shows her cross insecure , confused head... I stick to routine and familiar environments. 

Any advice please... I am feeling isolated and new to this......

/