Or does she not want to be friends anymore?

[ExtraPineappleExtraHam]

My friend and I have known eachother since we were 11 and roughly see eachother less than once a month. Sometimes we go out but usually she comes to me as her mum is just up the road. Yesterday she came over and just seemed quiet, like she didn't have anything to say.
To put the situation in context, dd is 2.4 and ds is 8 m.o. My house is chaos ATM as I've recently decided to change jobs, applied, been to interviews, got one, had to find childminders etc so haven't had much time for housework. My friend is very 'everything in it's place' and loves to clean.
She stayed in the lounge whilst I cooked us brunch in the kitchen. She didn't offer to help with the childcare or make much effort to help me. She left after an hour. She did exactly the same the time before.
I have a few theories
1.) She doesn't have anything to talk to me about/finds my life tedious.
2.) She is stunned by the chaos and her almost OCD kicks in and she can't stay in the house any longer than seems polite.
3.) As she often talks about having kids 'next year' or soon, my house is a reminder of what the reality of children is and she's not sure she wants to see the reality and not the Instagram version.
4.) she gets angry that I can't focus on her or talk to her properly without telling dd to get the potty or clearing blueberries off the floor.

All your suggestions are possible.
When you don't yet have children (and she might be trying to get pregnant already and not succeeding), others people's houses full of children and their stuff can be overwhelming.
Ditto trying to have a grown up conversation with a backdrop of Peppa Pig

I think Breakfast may be right. Before DD was born I found trying to have an adult conversation with the parent of a young child very frustrating, and being a tidy person myself I found visiting really chaotic houses unsettling. Child free people just don't get it I'm afraid.

I'm not judging you BTW because I am now a parent, but that is how it was for me.

Went out with some friends the other day and ended up talking to the one who hadn't brought DC. One with her dd complained that we hadn't had a chance to talk, but it's because all the focus was on the 3 sets of DC present. It's normal, but I would also have liked to talk without the constant pick up dropped food/baby wipe needed/cute moment when 2 yr old ordered from waitress/nappy change needed/child wanting to wander.

Maybe try for a child free outing? It's the same with pets, I find, they distract and no, I don't really want to worry about what they're doing while I'm at someone's house, hence mine are not involved in conversations!

Yep, could be any of those resons. Definitely try a child free meet up - it's impossible to talk to someone properly with a baby and toddler present.
In a few years time you'll have the polite older kids who will be entertaining her small kids while you both enjoy a peaceful brunch!!

It may not be about you specifically.
She may be going through a hard time herself or her OCD could be causing her anguish.

Don't take it personally and maybe arrange some time for just the two of you, if possible.

I agree, it's no fun trying to catch up with small children around. Maybe your friend has been quiet because she's got Stuff going on, but there's no way she can talk about in these circumstances.

I'd aim for some child free meet ups.

She didn't offer to help with the childcare or make much effort to help me. She left after an hour. She did exactly the same the time before.
For starters, if it's only happened on 2 occasions then it's more likely to be 5, she has a lot on her mind at the mo. But equally it could be 6, she feels that you only talk about yourself / your kids and take no notice of her issues or 7, doesn't want to be sorting out your kids when she's there to see you or 8, doesn't see that there is anything she can do to help make brunch (and realises that 1 hour isn't enough time to clean your house).

Got to be honest here. I have no kids and most of my friends do. Meeting up with them when they had newborns was fine, but when they had toddlers it was honestly quite hard to have any kind of conversation. We just spent the whole time entertaining the kids, or talking about the kids, and I'd go away feeling like we hadn't really talked at all. I didn't stop seeing my friends, but I didn't really feel like we really got much out of meeting up with the kids in tow and I don't think my friends asked me a single question about me or my life during that period or really listened to anything I was saying. Totally different now the kids are older of course and completely understandable that any parent with small children should be this way - I'm not criticising them at all. But it does change the dynamic a lot.

I always made time for my child free friends as I know how fucking annoying other people's little darlings can be.

And it was a good excuse to leave my kid/s

Have you asked her?

I agree with others try to arrange a child free meeting and ask if everything is ok with her.

I think you need to meet up without your DC present. It can be frustrating trying to talk to someone whose attention you don't have - I'm not blaming you, just saying how she might feel.

As a childless person I tend to agree with dolly, although I wouldn't be as extreme in saying that my friends never asked about me any more, just that it was impossible to have the great conversations and laughs our friendship was founded on with toddlers running around needing attention.