Juvenile pied flycatchers are all spotty/scaly - despite what the books may (fail to) tell you - so it's not one of those. But if it's early enough for it to have moulted (I've no idea), it might be a 1st-winter - though I doubt you'd be able to tell that, in these photos, from an adult female.
Thanks. My Guidebook (Collins) doesn‘t show juvenile plumage and an online image search didn‘t really help a lot.
As this was an really unexpected find (just 1km from my parents house and my father who is interested in birds wasn‘t aware of it) I was asking myself if it‘s just a single a female or if there might have been a breeding pair in the area.