I am assuming this is an Indian/subcontinent wedding, sorry if I am wrong. She can ask the parlour lady to apply her makeup that looks very natural. Neutral eyeshadow, minimal colour, something ‘my skin but better’ type of makeup. Your friend can practise on herself so that she can tell exactly what she wants. This way there won’t be much of difference with/without makeup.
I concur with pre wedding facial. Last time I got a fantastic facial in India. It was O2C2 by Cheryl. It left my face glowing for weeks. Plus there is a take home radiance lotion that can be used everyday after facial to prolong the benefits. She can have a facial once a month to maintain radiance.
However it is important to find a routine and stick to it which needs a lot of time and effort. Basics like exfoliation and moisturising always help.