As someone who has made many mistakes recently and over the past decade and some change, give yourself some credit and have some faith in your abilities to change and be a better person. I am working on earning my husband's trust back, and there are times when I want to give up. I have felt like I was sabotaging my chances at fully earning it back out of fear of losing it again.
If you walk away from Nisha, that will probably hurt her more than than anything else. My husband left for one day shy of two weeks, and I am one who never cries over living people. I actually shed tears and broke down. It was only 13 days, and it was the saddest 13 days of my life. When he walked in, I held on to him and vowed to right anything I had done to make him feel like leaving was the only option.
Keep working on your relationship with Nisha. Keep working towards earning her trust back. Someone on here said transparency is important. Tell her everything. Even those little things that seem irrelevant to you. I am learning this the hard way.
Sending you good vibes your way, and I am following your journey. I rarely comment on blogs, but I am doing better.