Oh Vee, you poor soul.
Maybe this visit back home wasn't such a good idea if it's made you feel restless and unhappy? Some folks come back from a visit to 'the old country' with the realisation that they've made the right decision to live in NZ but others, like you, come back very unsettled. It must be very difficult for you, being on your own and having your daughter's care to worry about. It can be hard enough bringing up a youngster when you have family support around you, so being on your own in NZ must put a lot of extra stress on you.
Whether your mum or your friend can immigrate is down to their individual circumstances. With your mum, you couldn't sponsor her to join you until you've held PR for 3 years. Apart from this, does she have any skills that NZ wants and is she under 55? If she'd had business experience she could possibly have applied for a LTBV and thought about starting up a business there, which might also have helped you in some way. If your mum isn't currently working, another option, although not ideal, would be for her to come to you on a Visit Visa for 6 months, then return to the UK for the rest of the year.
It really is sad that INZ makes it so difficult for parents to join their offspring in NZ but I guess they're just trying to protect the country from a rapid influx of older people who might be a burden on the already overstretched health service at some point. They are already complaining that there are too many older people in the country, so I'm very worried that something might be done in the near future to prevent the situation from getting worse.
I hope you can find some light at the end of the tunnel as it's a great pity that you seem to like being in NZ, but don't feel you can manage without some support. I would guess a lot of people feel like that and would really benefit from having at least their parents around them to help out. INZ and NZ must miss out on having many immigrants move back to their home countries purely because of missing family or needing their support.
Hope your walk on the beach helps to make you feel a bit better, even temporarily. If you want to toss ideas around on here, feel free and we'll see what we can do to help you feel better. Perhaps being back in NZ for a while will help to take the edge of your pain, although it won't directly affect your situation.