Never underestimate the capacity to misunderstand.
Language is a highly fickle thing. It takes years to learn, and a lifetime to master. There are many barriers to effective communication. Experience (along with age) is a big one. Children misunderstand what is said all the time. Mainly because they lack experience. They often take what they hear and place it into a context they understand. Most often, that means changing words and concepts they are unfamiliar with into something that sounds similar, but is quite incorrect. Flora does indeed have her work cut out for her, but she is patient. It will probably take her years to get Benni straight. For now, she just needs him to understand why pedophilia is wrong.
AAAAAAAAAAaaaaaaaaaaaaaaaaaaannnnnnnnnnnnndddddddddd here comes the light of comprehension in 4... 3... 2... 1... .
And if Tali is being abused in the way that Flora is telling Benni, it is a safe bet that Tali's father is prepping her so that he can fit inside her. For example... inserting an inflatable plug and using it to stretch and get her used to something big, taking her from behind like what has happened to Benni, oral, to name a few.
Benni just because Tali's father doesn't fit her now, doesn't mean that he is not looking for ways to make it easier for him to fit her. Hell, from what it sounds like, Benni may have had sex with Tali on occasion (that is based on what he has said to Flora in earlier strips), and possibly may have had sex with other kits as well. Not to mention, is Benni 100% certain that Tali's mother is not taking part in what is going on right now. That is the million dollar question at the moment.