I'm so sorry you feel so negative about the whole experience. Without being there it's impossible to gauge whether she was being negative or just trying to give you fair warning, but I wanted to come on and support you anyway.
Im a single mum of twins. I've been on my own since they were four months old when I left their father with literally just the clothes on my back. He became emotionally abusive at 3 months into my pregnancy and TBH I wish I'd left him then as at least I'd have been able to prepare for single motherhood a bit better. I had no support off him once the babies were born and may as well have been on my own. In the four months we were together, he never once bathed them or made up/sterilised a bottle for example. I left because I was fed up with this, at which point he turned physical and tried to strangle me. Needless to say he has supervised contact only.
Despite all this, I actually found being a single mother EASIER. With only my DC to concentrate on rather than another adult, it frees up a lot of time and mental energy. You have the added advantage of going in to this with your eyes wide open. You will have somewhere to live and be able to put coping strategies in place before your DTs are even born. You are going to be absolutely fine. 
I have very limited support. My family are mostly dead and those left do not live locally. I have good friends but they have families and lives of their own so were limited in the help they could offer, although one friend in particular was absolutely wonderful and I owe her a debt of gratitude I can never repay. It's been hard, but then it's equally hard for many mothers in marriages with limited support too. Having a partner is no guarantee that they'll actually be much help whether that's because of work or whatever.
It will be hard, but it's doable. Gather as much support as you possibly can and don't be afraid to ask for it, but you'll be fine, honestly. Because it was just the three of us, the bond I have with my DTs is amazing. Those early years where I could have cried with tiredness were a part of forming that bond. We got through it together.
Also, I know this may sound counter-intuitive, but for me work was an absolute godsend. It helped me keep some sort of routine (essential with twins IMO) and allowed me my own mummy-free identity and the chance to converse with adults about non-child-related things. Also having a dog helped as it forced me to get out of the house at least once daily (ideally twice). The exercise and fresh air was beneficial for us all, both physically and mentally. Little things like this can make a huge difference, so even if you can't get enough sleep (and you won't), make sure you get daily exercise and adult company. It will keep you sane.
Be prepared and aware of the pitfalls but put the doomsayers out of your mind. You are going to embark on an exciting new phase in your life and while having twins is challenging it is an amazing privilege. I wish you every joy and the best luck in the world.
Oh and I was walking my dog 6 miles a day right up to the day before I gave birth (induced) even though I was so big I had to give up driving because I couldn't fit behind the wheel of the car.
So you won't necessarily be tired and fed up at the end of your pregnancy either.
Congratulations! 