Assuming legally married or sufficient confidence to not have a break-up be a risk factor here. Gotta say that part.
To me, 4.5% and 5% (taxed) is not sufficiently different to be worth the mind space. If the world was perfect, you should do the CD thing. In real life, there could be a glitch or a mistake of timing that causes an issue with payment of a loan or an auto draft or something, you have to think about it and make sure it’s still paying and your CD is re-upping at a high enough interest rate etc. Not worth it in the slightest to me.