So, met a "friend", lets call her Sandra (name changed naturally!) at a post-natal group. We attend a few of the same groups together; however she works part time, I am a WAHM just starting to go back to the office now.
It is reasonable to say that we would not maybe naturally be friends if we'd met without children, but our DS's play nicely together (both just over 2) and we laugh together when we see each other. All a bit superficial, but pleasant, polite and all fine.
The local toddler group has been shut last week and this. I am part of the committee, so when it was an unexpected closure last week (expected this week due to holidays), I telephoned round to let people know, and suggested to Sandra that we take the boys out to the local soft play. She declined and said she was going to go food shopping instead - which is fair enough. I then said that I'd see her next week - forgetting it was the holidays.
Realised after the conversation my mistake, and texted her that I'd forgotten about the closure, and did she want to come round to mine instead. She agreed. I then texted back that I'd see her then, and I was off to take DS to the soft play.
Few minutes later, she then texted back that actually, she'd been invited by another friend to go, so she'd see me there. Bit 
about this, but fair enough. We then went to the soft play, and she spend the entire time not talking to me much - very monosyllabic and closed answers to my questions, but full on chatting to the other friend.
To today, and I'd posted on the toddler group website last week that I was offering my house for play (and tea/coffee), and a few other mums agreed it would be nice to come round (three in total).
Since last week, Sandra and I have been in contact via text and email (it's easier due to toddlers and work!), with no hint of anything bothering her - swapped recipes, asked after each others family - all normal to my eyes.
Fast forward to today, and I texted another friend to give her my address (I'd forgotten to do that!) and she texted back that she and Sandra were actually going to the soft play centre, was I not coming?
Turns out that Sandra has taken it upon herself to organise a trip out to the soft play. I was not invited - there is nothing on Facebook (group webpage) and no texts to me. I then texted her (on a random pretext) and she has only now told me about the trip; so while it may have been a genuine oversight (very unlikely), it feels more deliberate.
I've been dumped haven't I?
I actually feel quite angry and then terribly sad. I've gone to quite a bit of bother making cakes and things, and making sure that what I've done is suitable for her son who has allergies. I can't think of anything I've done to offend her enough that she would then try to sabotage (not the right word, but I can't think of what else to use) other people coming to mine.
I'm very shy, and I can't confront her, so I guess I'm just not going to do anything and back away. So sad...