My Dog Argentino is female dog aggressive. Is there anything that I can do to help change this?

I recently adopted a 9mo. old female Dogo Argentino. Sol was an owner surrender, the reason for this is complicated but I'll try to explain as briefly as possible. Sol's former owner runs a dog rescue agency in West Va. In addition to this the woman has four small children and a few animals (cats and dogs) that she keeps as pets obviously over-extended! One of her pets was a Dogo that she adopted. She loved the breed so much that she thought it would be a good idea to breed them. Thank goodness it didn't work out for her because she DOES NOT have the time or resources to properly breed such a powerful and dominant breed. Since she wasn't going to breed and was already over-extended she decided to adopt out Sol. I have always wanted a Dogo, love large athletic dogs and needed one for protection since I live by myself and run everyday. I need a dog that can keep up with me physically and that would visually be a deterrent to anyone with bad intentions. There is a Schutzhund class that meets about 20 minutes from where I live (Athens, Ga) and I have every intention of starting her on this training. She had very little 'face time' with her former owner so I have started her on some basic commands such as 'sit', 'down', and 'stay'. She is a very quick study. I have her eating in an un-used bedroom after me, sitting and waiting at the door, steps, and before we cross the street, there is no food or toy aggression, she tries to get on the couch and bed but readily accepts correction when I tell her 'off'. She has a high prey drive which has my cat a little upset but again she is quickly learning that the cat is not prey and to more or less ignore her. THE PROBLEM: dog aggression towards another female dog.

This appears to be her only flaw thus far and unfortunately I don't know how much of this I can change. Perhaps you will be able to tell me if there is something I can do to help this situation.

OTHER DOG BACKGROUND: a completely untrained beagle mix that is allowed to do whatever she wants and get away with it from everyone but me. This is my friends dog (she also has a 4mo male Bernese that Sol plays fine with) but I spend a lot of time with her because I have a fenced in yard so my friend drops them off to play everyday while she is at work. I am close enough that I come home on my lunch breaks and during this time I have been working on some basic obedience for her dogs too. Leila is out of control. She gets in the garbage, destroys things out of spite, eats food (MY FOOD) off of the table, sits wherever the hell she wants, and has bone aggression. The other day my dog tried to dominate Leila. There was a lot of growling and posturing and a few nips before it was broken up. Nothing major but an obvious cause for concern because my dog could easily eat her alive and though she is the most annoying dog ever I would never wish that on her. Now of course her owner thinks that this is all my dog's fault (and it might be that's why I'm writing). That my dog is overly aggressive/ dominant and that it?s a danger. Please correct me if I'm wrong but I think the problem lies more with her dog than with mine. I do think there are some problems with my interaction with both of them: for instance I'm the only one that tries to be pack leader over Leila and in my family (Sol and I) Sol is next in line I think that Sol thinks she is entitled to be dominant over Leila. This IS obviously dangerous because if Leila resists she is going to get her ass kicked or die. What can I do about this, how much of this can I control, will Schutzhund help? I love Sol and I hate for other people to look at her as a bully just because she is big and strong.

Carlina