AT that moment we were interrupted by the appearance of Madame Coutras, who had been paying visits. She came in, like a ship in full sail, an imposing creature, tall and stout, with an ample bust and an obesity girthed in alarmingly by straight-fronted corsets. She had a bold hooked nose and three chins. She held herself upright. She had not yielded for an instant to the enervating charm of the tropics, but contrariwise was more active, more worldly, more decided than anyone in a temperate clime would have thought it possible to be. She was evidently a copious talker, and now poured forth a breathless stream of anecdote and comment. She made the conversation we had just had seem far away and unreal.

这里girthed in alarmingly by...没看懂介词in和by. 还有一句than anyone in a temperate clime would have thought it possible to be. 麻烦老师讲解一下这个比较分句。

我记得should/would have thought 是约定俗成的说法，含义是：本来以为，原以为；而不是：本来应该想到，而实际没有想到的意思。那么，在本句中，这里的 would have thought 究竟该如何理解呢？- 这里是表可能性推测吗？