The first step is the most important: make sure you get the sizing right. The easiest way to do this is to simply ask, but if you're looking to surprise them that might not work.
In that case note the bra and panty size from her existing lingerie. Also take note of the colours and style; this will help with your decision-making when it comes to choosing something you want her to love.
If you're still struggling, feel free to contact our customer service team. We're here to help.