My cat needs to gain weight quickly

First she was at the vets yesterday and they let us take her home before you say anything. I'm typing this quick so don't mind if I'm all scrambled but I need high calorie food ideas for her to fatten her up, she is getting tons of calorie supplements already and is eating kitten food. She was a stray who adopted up who when she started getting a big stomach and we took her to the vet we were praying it was worms but we knew it was kittens deep down, she had 6 kittens and they're sucking the life out of her. Were trying to bottle feed them so advice on that would help too because they're not taking it. She's about 7-8 months old. Please help us out the babies are killing her.

(I'm a minor but my mom will do anything for that cat, I'm in Ireland, she was at the vet yesterday but if nothing happens by around Saturday we might just take her in to put her on a drip, she's 7-8 months old, she can't be spayed for 6 more weeks, we can't really afford vet care but we'll try)