I envy your wife "having" to fly to FLR for business. I want that job!

Anyhow, since you want to avoid UA/Ted, your options are pretty much limited to:

1) US to PHL or CLT; then
2) US to FRA and MUC or LH to FRA (if step 1 is through PHL) or US to FRA and LH to MUC (if step 1 is through CLT); then
3) LH to FLR.

I see from the * A flight search feature that LH flies Dash 8s from MUC-FLR but does fly Avro RJ45s from FRA to FLR, so if it was me, I would fly through FRA to avoid a prop plane. I've flown Avro RJ45s on UA and they are actually decent.

So that leaves us with taking either US CLT-FRA or PHL-FRA or LH from PHL-FRA on the transatlantic segment. Having tried both, I like LH's transatlantic C better, so I would do TPA-PHL(US)-FRA(LH)-FLR(LH). I don't know whether LH has the "new" C class on PHL-FRA, but if they do that's all the more reason.

One thing though. If your wife has to leave after 12:00 from FLR, then she would have to have an itinerary including UA. It would be FLR-FRA(LH)-IAD(UA)-TPA(Ted), according to the * A flight search feature.

I hope this helps.