Or someone is running and trips over her. Something like 800,000 kids get bitten badly enough to need medical attention every year, mostly family or friend dogs, and mostly just because of miscommunication or accidents. I will definitely climb on a soapbox for dog bite safety!
@the OP, any time, seriously. Raising and handling good dogs is a skill, like any other. It's hard to pick up a musical instrument and figure out how to play it, too–it's much easier and a whole lot more fun to find folks to practice and play with! Also, I'm guessing whatever her background, who ever ushered her into the world probably wasn't really a craftsman when it came to puppy handling. Add to that inexperienced early handling at home, and it's no wonder that some huge percentage of random-bred dogs end up recycling through the shelter/rescue system multiple times, and starting about this age, too.
Are we still playing Guess the Breed? I spy... French bulldog with some terrier and a smattering of something lankier? We see a lot of dogs that look like that here. We call them "Southern Yard Scrappers". A little bulldog, a little feist, a little "???". 
I like them a lot!
ETA: At the risk of overstaying my welcome, or offering stuff you already know, I wanted to clarify my first response. Please keep in mind that this is random internet advice from a stranger--no one who hasn't seen your dog can give you specific advice on how to fix the issues--but in the interest of safety, I wanted to clarify the" setting rules" stuff. I do not mean to provoke confrontation. If she is in the middle of doing something unwanted, don't directly confront her. It she has "learned" that aggression is how to communicate, and you first let her get on the couch, then try to make her get off it, she will only escalate her learned responses.
This is how I, personally, would manage a dog of unknown background until I got some hands-on help, IF I felt comfortable putting a leash on her and touching her. I would keep her leashed to me at all times. Keep a towel or cheapie blanket or a carpet sample in any room where you might be for a while, it's now her "job" to stay quietly on her place. Make sure her needs are provided, she eats, drinks, and relieves herself on a schedule (feed her in the am, let her drink, take her out to potty, then to her "place" next to you, wherever you are. When she gets to her "place", and is calm, magically make a toy appear. Not something too exciting, but something she will play with in her spot. If you can't keep her with you, or there's too much kid activity to be safe, contain her in a play pen or crate where you can keep an eye on her.
It's helpful to exercise with her first thing in the morning, there's that old joke that a tired dog is a good dog. If you get a good romp in, she's more likely to stay quietly in her place. Also it's helpful to name things for her. When you offer her water, ask, do you want water? And name " water" as she drinks. Same with going potty. After she eats and drinks, do you want to go potty? Take her out, and as she squats and starts to go, say "good girl, go potty!" When she goes into her crate, pen, or place mat, name those things for her and give her a toy to reward her and keep her busy.
Again, only if you feel safe interacting with her. Keeping her leashed to you or crated/penned when you're not able helps you keep everyone safe until you get some hands-on help. I was concerned that what I said before would sound like I meant you to escalate conflicts--better to not let the behavior happen at all. Just set her up for success and reward her for it, and find a good trainer to help with the specifics. I hope that makes sense... And whatever you do, do not do anything that feels unsafe!
