Simmons is part of a consortium including Emmanuel College, Wheelock College, Mass Art, Mass college of pharmacy, and the Wentworth Institute of Technology. You can take classes at those schools, all of which are coed.
Lesley and Suffolk have different vibes, imo. Lesley is a lot more open to alternative, artistic types because of its College of Art and Design, whereas Suffolk’s business program and law school lend it a more pre-professional feeling. Lesley is located in Cambridge. Its campus is a bit more spread out that Suffolk’s, but not by much. But Suffolk is right on the Common, near the theatre district, and you can easily walk to some of Boston’s attractions from there. So that’s nice too. I don’t think one is more rigorous than the other; they’re both solid safeties where you can receive a good education. As you’ve noticed, you would be a contender for merit at both, so if you’re open to both of them, I would suggest applying and seeing how the FA packages turn out.
I love Wellesley too; I almost went there, so I’m biased towards it 
However, if your goal is to be IN Boston, you should factor in that it’s about a forty-minute bus ride away, in a very quiet, rich suburb. It is free to apply to, though, if you do end up taking subject tests.
I really wouldn’t push Emerson to someone who wants to major in English, not the specific degree they offer. They don’t offer a whole lot of majors, so if you ended up not liking that, you would basically be forced to transfer. And they’re notoriously bad with financial aid.