wildebube wrote:
EVERY time I have tried to talk to her about ANYTHING serious, sex, money, potential career changes, …, anything, she just clams up.
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How would it work if you opened with, "I need to tell you something. I'm not looking for a response from you. I just need you to hear me, think about it, and respond later."

Maybe she feels pressured by the convo and that would relieve it. It could be that you process things quicker than her and she needs time to gather her thoughts. You could close by thanking her for listening, restate the importance of it to you, and give her a kiss.