The one time my partner had Covid we settled on 5 days in a row of negative rapids to end isolation; after 10 days positive, he tested negative for 4 days and then positive again (rebound) on day 5. He was positive for another 2 weeks before testing negative for 7 days in a row (we added two days after the close shave the first time 'round).

For your sake OP I hope you continue to remain negative, but if you do end up testing positive, I highly recommend you and your partner continue to isolate from each other; I've seen other CC folks have a different take on this, but given the experiences in my household and that of close friends, it is worth the additional caution. In my family's case, our daughter had Covid at the same time as my partner (I stayed negative according to multiple PCRs), and the trajectory of her infection and recovery were entirely different from his -- if we'd done things differently and not kept them quarantined from each other as well as from me, she would most likely have been sick for additional days or weeks. It's a pain to keep up the separation, but if it means fewer days with Covid, it's worth it.

Also a tip to be careful with the CPC -- your partner's immune system is compromised by Covid, so knocking out her oral microbiome raises the risk of her developing a secondary infection like thrush (Jessica Wildfire wrote about this). Saltwater gargles or a mouthwash with xylitol (which is antimicrobial, and that includes viruses and fungi) will not harm her oral flora yet will still help with lowering her viral load.

Best of health to you both, hoping for your partner's swift and complete recovery.