A precedes the noun with gustar when naming the person or persons being pleased in this case, Cecilia is the proper noun. It could be, A mis amigos, A mis primos etc. This applies to other verbs used like gustar, encantar, faltar etc. Cynthia at Light Speed refers to these as impersonal verbs. The Light Speed video about también and tampoco addresses the need for a when agreeing or disagreeing with gustar. If you remember, and I usually don't think this out, I just use it, fútbol is the subject and Cecilia is the object when using gustar. Which is what your correct guess was. That is why I don't think it out! Hope this helps.