I would have thought that Darwinism would have clarified these electrical threads by now. It is a wonder many of these posters haven't fried themselves by now.
An off the shelf 30 to 50 adapter will be perfectly safe. The only way you would create a fire hazard is if an adapter is used a bridge between two higher rated appliances and services. I.E a 50 amp RV, an adapter to 30 amps, a 30 amp extension cord and then an adapter up to 50 amps to plug it into a 50 amp outlet. That would create a fire hazard in either the adapters or the cord.
Now in this post we have all sorts of problems. First, the OP said the plug end on the RV cord is a female. If that is the case, there is something really wrong and an electrician should be the first and only stop the OP should make.
She said she is only getting one leg of power. If that is actually happening and not just mis-speak by the OP, the rig is a 50 amp rig. If they have lost a leg of power, it is most likely the adapter since a properly built adapter will supply power to both legs. The easiest way to check is to find a 50 amp pedestal and connect the rig. If both legs work, it is the adapter. If only one works, it is a problem with the cord or the transfer switch. But I am very concerned about what they mean by the "shore side is female" If it means the rig has a detachable power cord and the female end of the cord plugs into the side of the RV with a twist lock and possibly a threaded ring to secure it, Marinco style, no problem. If it means the plug on the end of the cord that normally attaches to the power box is female, big problem.