Different rules for different dogs.

I really need help. So I had a 14 lbs chihuahua. He’s been allowed on the bed/couch for the 8 years I’ve had him. It’s never been a problem because he doesn’t like getting dirty and he’s small. My boyfriend really wanted a big dog so we got big dog. And she… is a big deal. She’s fluffy and loves getting muddy…. And she’s also been allowed on the furniture. Guys I’m losing my mind with all the dirt and debris and fur. I can’t fucking do it. I love her, she’s not going anywhere but I cannot continue with her on the furniture. So, my question is, can we have different rules for different dogs? Can my little guy continue being on the couch/bed while we train her off of the furniture?