Another spiderwasp and again a new garden species, a female Priocnemis fennica [1,2]. This is an uncommon wasp in the Netherlands [3].
She was foraging on and around the window frame probably looking for spiders I assume.
See also the approved pbservation on Waarneming.nl.

The species can be identified using the following characters [2]:
- inner eye edge parallel (photo 4)
- second discoidal cell front wing without sag (photo 5)
- thorns on shin 3 equal in length and spacing (photo 2, 3)
- front pronotum rounded (photo 2, 4)
- first abdominal segment not petiolate (photo 2)
- shin 3 dorsally with scales, ventrally seen sawtoothed (photo 2, 3)
- tip radial cell pointed (photo 5)
- propodeum hairless and smooth (photo 2)
- dark pigmented frontwing with a bright spot at the tip (photo 1, 3, 4)
- first tergites red (photo 2)
- claw with side tooth closely to the end tooth and equal in size (photo 6)
- antennal members slender, members 5 to 8 at least 2,5x longer then wide (photo 1, 3)
- angle between ocelli acute (photo 4)
Literature
1 Nederlands Soortenregister2 Nieuwenhuijsen, H., 2008. De spinnendoders van Nederland (Hymenoptera: Pompilidae). Jeugdbondsuitgeverij.
3 Waarneming.nl
Added link to Waarneming.nl approved observation and identification characters