Does Vex make opponent pay 1 extra power and 1 extra energy?

Yes, Vex, Cheerless makes your opponent pay 1 extra Energy and 1 extra Power for their spells while she is in combat.

According to the card text for Vex, Cheerless:

"While I'm in combat, friendly spells cost [1] [A] less to a minimum of [1], and enemy spells cost [1] [A] more."

In Riftbound, the symbol [A] represents a Power of any domain. Therefore, Vex's ability increases the cost of enemy spells by 1 Energy and 1 Power.

Important Nuances:

• Combat Requirement: This effect is only active while Vex is in combat at a battlefield. If she is not in combat, the cost increase does not apply.
• Hidden Cards: As noted in RiftJudge FAQ #620, this cost increase applies to hidden cards as well. The game sets the hidden card's cost to 0 first, and then Vex's cost increase is applied, resulting in a final cost of 1 Energy and 1 Power.
• Repeat Costs: According to RiftJudge FAQ #2161, Vex's ability does not affect "Repeat" costs, as those are considered optional additional costs separate from the base spell cost.