The dogs, not thought to be a banned breed, are destroyed after attacking the woman aged in her 70s.
The law around dog attacks has been tightened, with owners now facing unlimited fines.
Officers were called to a street in Southport after they were told two dogs were on the loose.
A cavapoo was killed by two other dogs while being walked on a Banbury street on Friday.
XL bully dogs were banned two years ago - BBC News looks at why attacks may still be happening.
Woodside Animal Welfare Sanctuary is urging pet owners to spay or neuter their dogs.
Two other alpacas are treated by vets for facial injuries as two dogs are seized, police say.
Three pregnant sheep have been killed by what police believe to be a dog.
John McColl died a month after the attack by the dog, which had to be shot 10 times by police officers.
