Once I get into Oklahoma - I just follow US-70 east. Neither my Garmin nor my Rand-McNally have tried to send me down a dirt road.
The maps show a 'US-70 Bypass' across north of Idabel - which apparently isn't the route the bypass actually took. Since the state highway department has never corrected their data, it appears on the GPS.
Or she may be talking about FM-37 in Texas from Clarksville to Idabel. Which is a fine road to travel on with an RV - at least it was about 18 months ago when I last drove it.
As far as getting to Oklahoma - you probably know the DFW freeway system - and the construction on US-380 between Decatur and Denton, also in Farmersville, and the couple dozen stoplights between Denton and McKinney.
You can go up to US-82 and over to Paris, or through the metroplex and out I-30 to Greenville / Commerce and up TX-24 / TX-19 to Paris and US-271 to Hugo, OK.