Well, the foreign earned income exclusion goes up to $112k for 2022. If she earns more than that, she won't be able to take it. For a high tax country like the UK, the tax credit can be more effective, anway.
Bottom line: getting the taxes right will greatly overshadow the benefit of an IRA contribution--it's a side effect, not the primary goal to shoot for. But if you or she had not considered this was a possibility, then by all means take advantage of the US's desire for global taxation to shelter some more money, in familiar ways. :)