Agressive female cotton de tulear - help

We have just got a 6 moth old female coton de tulear 2 weeks ago and we are finding (unpleasantly surprised by it) that she is displaying a lot of agressive behaviour. We start preofessional trainer sessions in two weeks but are in the dark about what to do until then.

She growls/barks at virtually every sound she hears inside our appartment. Wheter it comes from outside or inside (even like from brushing teeth). When we go out, it is worse. She growls or barks at people, dogs, birds, cars, anything, if they are close enough she will try to jump into them (she would even pick fights with dogs way bigger than her). Then when the dog reacts she will hide behind me. She barks and growls at passeers by if we go somewhere and sit down to eat or simply relax. We have no idea why she is like that. We also can't quite figure out wheter it is fear agression, dog on dog agresion, territorial agression...or a mix. She does come from a breeder with a large pack and maybe she was not given enough attention. No idea.

We are trying to give her lots of treets but unless we literally stuff her face, she will growl, jup into dogs, bark crazily.... We are being firm, we tell her No, we reward her when she is good, we try to distract her with toys but she won't budge.

Any ideas what type of agression this might be, what the possible cause might be and what to do untill we start our sessions?

Also, do you think spaying her would help? We are seriously considering doing it asap.

No spaying generally makes aggression worse in females.If she's 6 months old where has she been until now? Did the breeder keep her back because she was running her on to show? She just sounds seriously under socialised to everything, was she living in the house with the breeder or in a kennel or outhouse as is frequently the case with breeders with a large number of dogs.
Also stuffing her full of treats when she's growling etc is rewarding her for her poor behaviour, so tbh I'd stop that.

The dogs all live in the first floor of the house with the owner. The breeder said noone would take her because everyone wants males. To my knowledge she was not on shows.

We only stuff her face if we manage to do it before she growls or barks.

It definitely sounds like lack of socialisation rather than straight forward aggression. I think the breeder might have been quite economical with the truth tbh. If it was just a case of no one wanting a bitch the breeder would have put the effort in to socialise her to give her a good start in life. Did the breeder give any indication of her behaviour issues?