"Should" is here used in a subordinate clause after an adjective expressing a personal reaction to something. It's surprising that my mother should say that to you (she's usually quite reserved). You can also use "would" instead of "should" or you can omit "should": It's surprising that my mother would say that to you.
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jooneyIt's funny you should mention that. ... And what does the whole sentence mean?A less literal paraphrase is