I know it's probably not incredibly helpful, but it depends on your circumstances.
If you're paying for your flight to the US, would it cause financial pressure? For most expats, it takes a while to get a job in the UK because they do not have any UK work experience. Are you in a situation where you could comfortably survive on one salary for a while, or would you want to keep as much money aside as possible?
Would you prefer to use the money for something else? (e.g. going on a mini holiday break after she arrives, the cost of her flight to the UK when the visa is approved, being able to ship a few extra things to the UK, driving lessons, etc)
Is her intended travel date still a few months in the future (so even if the visa is approved tomorrow, it probably wouldn't be valid for a while and you would otherwise be separated for a long time), or are you at the point where once the visa is approved, she's going to move immediately?
(and just as an FYI, like the UK, any kind of work is not permitted in the US while as a visitor; I know someone who got into trouble for that)