Okay, if it were me I'd try isolating her inside where it's coolest until she's totally calm and relaxed with fresh, cool water then watch her. If, amidst that, she's still red and sporadically panting I'd start checking crop, feeling belly, checking vent and skin, etc (the full physical).
Good plan, cool her down and see then. You will need to wait for her to calm down as stress will cause a similar reaction as heat.