What are you talking about? What red flags? They might not be red flags at all, except that they irritate you. Did she not tell you that she had a service dog? She might not have had the dog yet, they take time to train and some groups that get these dogs for the disabled give more notice than others. You don’t have the right of refusal, your acceptance isn’t required. You wouldn’t be able to tell someone that they couldn’t have their wheelchair, so you can’t say that they can’t have a service animal.
So exactly what red flags? Without that information no one can tell you if the problem is the tenant or if it is just you being ignorant of the laws. My bet is the problem is you. Go ahead, try to evict your disabled tenant, then they can counter sue you for discrimination and violating the ADA. I hope they get a good attorney because if there has been any harassment they should be hauling you into federal court instead of state, where they can sue for a whole lot more money.