Just say "Let's raincheck then" and you can choose to continue the convo as normal or cut if off "Have a good Friday and talk soon". Personally wouldn't take girls out on activity dates before banging, few reasons but mainly just too platonic and not really conducive to building up a solid interaction.

"Just tell her ur going on a date with a super hot guy, im sure shell understand"

That was a poor hard close. you didn't even know if she was free on Sunday. Take a look at some of the videos on guides on texting on the yt and my free website