90 gallons could be anything, for example, a high tank, but with not a lot of territory. What are the dimensions of your tank? I think a slightly longer tank, with more territory and more swimming places you have a chance two angels might work out. Just like Nereefpat said.
But I think it's a risk, it could go right, or it could go wrong. You gotta have luck that both the fish are a bit peaceful.
I wouldn't dare to put another angel with my bispinosa. She's a feisty one.