Once he takes Wolfsbane Potion, he'd be no danger to her.

When Lupin takes his Wolfsbane Potion, it makes him not a danger to others. It lets him keep his mind, and while he was at Hogwarts, he'd be able to curl up in his office and wait until it was over.

“The Potion that Professor Snape has been making for me is a very recent discovery. It makes me safe, you see. As long as I take it in the week preceding the full moon, I keep my mind when I transform … I am able to curl up in my office, a harmless wolf, and wait for the moon to wane again.” _{^{- Harry Potter and the Prisoner of Azkaban, Chapter 18 (Moony, Wormtail, Padfoot and Prongs)}}

He'd be able to do something similar while living with Tonks. He could go into a spare room and wait out his transformation the same way he did at Hogwarts. He'd still have his mind, so he wouldn't try to escape and eat Tonks, or end up destroying the house.

Once he takes Wolfsbane Potion, he'd be no danger to her.

When Lupin takes his Wolfsbane Potion, it makes him not a danger to others. It lets him keep his mind, and while he was at Hogwarts, he'd be able to curl up in his office and wait until it was over.

“The Potion that Professor Snape has been making for me is a very recent discovery. It makes me safe, you see. As long as I take it in the week preceding the full moon, I keep my mind when I transform … I am able to curl up in my office, a harmless wolf, and wait for the moon to wane again.”  
_{^{- Harry Potter and the Prisoner of Azkaban, Chapter 18 (Moony, Wormtail, Padfoot and Prongs)}}

He'd be able to do something similar while living with Tonks. He could go into a spare room and wait out his transformation the same way he did at Hogwarts. He'd still have his mind, so he wouldn't try to escape and eat Tonks, or end up destroying the house.

#Once he takes Wolfsbane Potion, he'd be no danger to her.

When Lupin takes his Wolfsbane Potion, it makes him not a danger to others. It lets him keep his mind, and while he was at Hogwarts, he'd be able to curl up in his office and wait until it was over.

“The Potion that Professor Snape has been making for me is a very recent discovery. It makes me safe, you see. As long as I take it in the week preceding the full moon, I keep my mind when I transform … I am able to curl up in my office, a harmless wolf, and wait for the moon to wane again.” _{^{- Harry Potter and the Prisoner of Azkaban, Chapter 18 (Moony, Wormtail, Padfoot and Prongs)}}

He'd be able to do something similar while living with Tonks. He could go into a spare room and wait out his transformation the same way he did at Hogwarts. He'd still have his mind, so he wouldn't try to escape and eat Tonks, or end up destroying the house.

Once he takes Wolfsbane Potion, he'd be no danger to her.

When Lupin takes his Wolfsbane Potion, it makes him not a danger to others. It lets him keep his mind, and while he was at Hogwarts, he'd be able to curl up in his office and wait until it was over.

“The Potion that Professor Snape has been making for me is a very recent discovery. It makes me safe, you see. As long as I take it in the week preceding the full moon, I keep my mind when I transform … I am able to curl up in my office, a harmless wolf, and wait for the moon to wane again.” _{^{- Harry Potter and the Prisoner of Azkaban, Chapter 18 (Moony, Wormtail, Padfoot and Prongs)}}

He'd be able to do something similar while living with Tonks. He could go into a spare room and wait out his transformation the same way he did at Hogwarts. He'd still have his mind, so he wouldn't try to escape and eat Tonks, or end up destroying the house.