I have had vasospasms before breastfeeding and found this info today on Yerba mate tea.

Well, there’s more to yerba mate than just caffeine/mateine. Take theobromine, for example. Theobromine, best known for being the primary alkaloid in cacao and highly toxic to dogs, exerts a smoother, longer-lasting stimulatory effect. Whereas caffeine is a vasoconstrictor, theobromine is an effective vasodilator, relaxing the smooth muscle in blood vessels and allowing better blood flow. It’s present in varying amounts in each variety of yerba mate, some with caffeine/theobromine ratios of 10:1 and others with ratios of 2:1, and can actually lower blood pressure in hypertensive individuals. Pure caffeine has the tendency to increase blood pressure. It’s plausible, then, that various ratios of theobromine and caffeine have different effects paired together than either do alone.

So, it could help with vasospasms!