Thanks for the query.
Since she is having on and off fever
, better to chart the exact temperature twice daily before consulting your Obstetrician.
Once infection is ruled out, 2nd trimester is the safest period to travel in low risk women.
During travel ask her keep her feet at a higher level. walk for 5min every 30 min.
There is no harm in travelling provided BPP of the fetus is normal before travel.
Hope this helps.regards,