I was able to measure the spider, by taking a pic with a pen in the same plane. Rough dimensions:

• body, length: 15mm
• body, width: 8mm
• backmost leg: 23mm

And due to better lighting I also managed to take a clearer picture:

Sadly the position doesn’t let me take an upside view pic. I think that she wants belly rubs.

@tobogganablaze@lemmus.org kindly identified it already (Argiope argentata), so I’m sharing this mostly as fluff.