I feel really sad for my child plus myself! I’m feeling really low. Quite honestly I have no friends and it’s hard making friends as an adult. They all seem to be mingling and getting friendly why is it so hard for me? If my child was in sane class I would also have gotten to be in their little group!
As a pp said, this is nothing to do with your daughter. Bluntly, these are your issues, and you need to own them and deal with them, and stop projecting them onto your young child.
If only two children from nursery are attending her school, it's mad to wail that they're 'all' in the other reception class - it sounds like some kind of persecution complex!
And you are complaining about other parents moving away from you once they found out your child wasn't in their child's class, yet you are also differentiating the parents on the basis of 'my child's class' vs 'the other class'!
Honestly, OP, you need to calm down and deal with your own issues. If you regularly experience difficulties with friendships, the clue may be in your own behaviour. From the way you're describing your attitude on here, you're coming across as desperate, needy, and alert to the slightest sign that there's an 'in-group' you're not in.
Separate your DD's social life from your own. She's going to be tired and overwhelmed at the start of reception, anyway, and isn't going to be on some friendship campaign, or on the look out for 'exclusions'. When she starts to make friends, by all means invite them for a playdate, or suggest on the class WhatsApp, if there is one, a general trip to the park after school?
But you need to address your own loneliness separately. It maybe that you will find friends among the other parents, but it is far less likely to happen with that over-the-top 'No one wants to be my friend!' attitude.