Loved ones setting you up for failure!

Phrick

Just make it clear that you're working out and she is welcome to join, but that it is your plan for the day. If she isn't interested in working out, schedule a separate time to hangout sans workout.

I was thinking sort of along the same lines.

Be honest with your friend. Tell her that her workouts aren't really workouts, they're an excuse to socialize. And while you love to socialize, your workouts have to come first if you're going to meet your goals. Tell her you're going to do your workout with or without her, then ask if she'd like to get together before or after your workout, and whether she wants to hang out together at the gym or someplace else.

The part I bolded above - do that only if you are prepared to lose the friendship completely! A better approach would be to leave off the part that basically accuses her of not being committed and not trying, and just say "I love to hang out with you but at the gym I need to focus so how about we meet after at ___ for ___?"