This book was written in the 60's and Mary Stewart has a very '60's view of the role of women in society.
Vanessa, spends all that time to get a veterinary degree yet as a married woman, only uses that degree when her husband is out of town. It just isn't the "done" thing for a married woman to work! And she's very trusting of her husband even when most signs point to infidelity at worst and lying at best.
This period-typical view should make the book feel very dated, yet somehow it just feels very quaint instead. I guess it's technically the same thing, but to me one has more negative connotations than the other. And normally a woman thinking about how fragile females are and how they like to be cosseted would bother me. But for whatever reason, it didn't bug me in the slightest this time.
Maybe it's because of regardless of what Stewart thinks a woman's role should be, she never once doubts that Vanessa is a capable woman. We're given a heroine that doesn't mind clinging to her husband for reassurance and support - but only after she's already rescued herself and mostly resolved whatever situation she was in. She's certainly not a shrinking violet or a damsel in distress.