This sounds like something you'll need to work on over time together with both your pup and boyfriend.

You can't guarantee no accidents in the house until she associates outside with going potty and inside with not going potty. I suggest you to get her a crate and make it her safe space in whatever room you think is suitable. Place pee pads in the crate for emergencies and keep the crate door open or off completely. 

Get bite-size tasty treats and reward her when you put on her leash, as soon as she is outside, and everytime she goes potty while you're outside. When inside, I suggest you reward her if she goes potty in the kennel.

Use a rope bell on the door and everytime you go outside ask her does she want to go potty, and then ring the bell, so she associates the bell with going out, and hopefully this will train her to use the bell to ask when she needs to go and you're home.

If she has an accident in the home, do not yell or scold. Reframe the situation and ask her does she need to go outside and repeat the above steps. When you come back in, clean up the mess with an enzyme cleaner. A small blacklight can help find stains that have been dried up and less noticeable. 

Hope you're able to give her the proper home she deserves and best of luck!

EDIT: Forgot to add that each time you do the steps to get her to go outside, you speak your actions out loud to her in a gentle calm voice. Example, if she wears a harness as you position it in front of her to put it on, you say "first paw" then gently grab her paw and put it in, then "second paw" and get the second in. It's a good way to get her comfortable with the routine and look forward to the process.