Hair and Makeup Payment

It is not good to rely on pictures on a site like Instagram for a makeup artist since there is no assurance that the pictures represent that person's work. You could try searches on the photos using the Microsoft Edge browser that will show an option at the top of the image that will let you do that search pretty quickly. You would be checking if the pictures are from other makeup artists. Also though, the lack of a contract is an issue since no agreements have been established and no person has obligated to do the work.

Regarding the payments, it is typical to pay for services before the event since a makeup artist or any other vendor does not know if customers will complete the payments.

I would request a written contract from her if you're planning to book her. That would give you a good chance at getting your money back if she doesn't show up on the wedding day. I don't think it's unheard of for vendors to want payment by the day before - some vendors, such as photographers or florists, sometimes require payment in full a month before the wedding. But the lack of reviews is a concern. How long has this person been working in the wedding industry? Are you confident that the photos you see on her Instagram page are actually photos of her work? If she's been in industry for a while, I would think that someone would have left reviews somewhere (on Google, Facebook, The Knot, WeddingWire, etc). If she's not open to signing a legally binding contract, I would find a different makeup artist.