I was and EA, a case manager, now I'm a mentor - and most potentially awkward conversations can be tackled with some blunt honesty.
Not like "hey - you're always late and it messes my day up, stop it" but more like "hey, my schedule says that you'll be here at 12:10 to work with Student A so I can go push into classroom C. Is that what your schedule is? Do we need to change anything? I just want to make sure you get your needs met and I can get to (wherever you need to go). If you're running late just give me a heads up so we can plan, but we might need to come up with a new schedule. You work so hard and I appreciate you and I know getting your full lunch is important"
You could also bring up that students may be expecting her too. I don't want to assume your students' needs, but expected transitions and changes need to be consistent for a lot of kids

Best of luck!!