In retrospect, I can't believe I said it. I thought she was asking me an honest question, so I gave her an honest answer. How was I supposed to know she'd get so angry? She asked me if I'd like to solve equations with her sister, and I casually said "Yes, apparently she's really good at it." Apparently this was the point where the limit of love was discontinuous. If she felt threatened by her sister's quantifiers and her skills with solving equations, then that was something she would have to deal with.
If the fact that we spanned every horizontal plane on her bed given that her parents weren't home, and not once did I imagine spanning her sister's bed wasn't enough for her, then perhaps what I once thought was provable was, in fact, false. The very thought increased the nullity of the matrix of my heart. Quickly discarding such negative notions, I told myself that the two of us will converge one day. If only x was large enough for me to know for certain.