"heard about/of you" and "heard from you" mean very different things. Are both correct, depending on context or is one really meant over the other?
Yes, exactly, they are both correct. There is no way of knowing whether the "de" means of or from without the context.
If the intended meaning were "she has not heard of you", I think this could be clarified in Spanish by saying "ella no ha oido hablar de ti". But I yes, I think "ella no ha oido de ti" could also mean "she has not heard of you".
"Te" is an object pronoun that can be acted on or receive the action on an object.
Yo te habla: I speak to you. Yo te doy un regalo: I give you a gift.
"Ti" is used in prepositional phrases, along with the pronoun mí (to replace yo). Fortunately for all of us, the rest of them are the very same as subject pronouns... de mí, ti, usted, él, ella; de nosotros/as, vosotros/as, ustedes, ellos, ellas. Of course, don't forget conmigo and contigo.
Tú is a subject pronoun. Ti is a stand-alone object pronoun that can be part of a prepositional phrase. The difference is the same as the one between English "he" and "him". "He" is a subject, "him" is an object.
The slightly weirder thing is te. Te is an object clitic. It gets called a pronoun, but a fair number of linguists don't think it's a pronoun, or even really a word. All of the clitic pronouns (me, te, lo, la, le, se, nos, os, los, las, les) are actually special forms of verb inflection.
It is not uncommon to see both the actual pronoun, and the clitic, deployed in the same sentence, for emphasis. For instance: A ti no te gusta correr. Pero a mí, me gusta. You don't like to run. But me, I like it.
'Heard' and 'listened' have different meanings. In this sentence that person has not contacted them in a while. 'Escuchar' means to listen. 'No te ha escuchado' means the person is there but not listening/paying attention to you.