Chihuahua labour, 6lb mum 5lb dad?

oki, so im worried ( i know i should be ) before everyone starts calling me a stupid back yard breeder hear me out.... i rescued a little chihuahua at 6Month old from a puppy farm, i was told she had been spayed!!! i am not a breeder nor do i want to breed nor did i want this to happen,shes now 1 and a half( to me she looks like chi cross jack) anyways, i also have another female that i had spayed as soon as i rescued her as she wasn't done, we also have a boy chi, not done :/ we got him from a pup and fell in love with the breed, ive always been against breeding because of the dogs left with no homes :( that's why i rescued instead of buying the other 2)..... anyways thing is shes pregnant!!! long story short i didn't realize she had even been with the boy dog i have nor did i realize she was in season because i didn't look out for it thinking she was spayed, .... ive done some Research and seen most people say they need c sections? ( i will take her for one if at any point she struggles~) but is this always the case? shes about 3 and a half kilograms and the dad is 2 and a half......not sure about parents and i know this is also a big part, please dint call me stupid and irresponsible because i already know. and it definitely wont be happening again... thanks .... any info is very much appreciated. x also.... i am responsible and i will take her right to the vets during labour if need be....i would never risk her life. iv put some money away now as-well for emergency treatment should we need to take her.