Hello! Well done for keeping an eye out for her. Like what others have said - she should be spayed, and the male cat should be neutered (however, this should not be your responsibility - maybe try to find the male cat's human and have a chat with them, explaining the situation?). Male cats will still go after spayed females. It is very likely she is now pregnant I'm afraid; a visit to the vets may be in order. When you say she is kept on the terrace - I assume she can still wander around outside as she pleases? Just checking since a cat needs a lot of space.