I have noticed a lot of guys worrying too much about lowering values or demonstrating higher values..! Why stop if the texting is going well, just because you worry you are showing her lower values? I personally dont think that by purposely not continuing in the text messages, a girl will consider you as having lower value unless you sound desperate and needy but a funny banter like your text transcripot above is surely not showing any of that desperation...! If I need to end it, I just say "Im off now, will text you later" etc..!

Good luck, she seems a nice girl!!