She was photographed with a beau a few years ago: handsome, long hair tatooed singer/artist type.
Circumstantial indicators may be there, but I hope that you are wrong.
If she wanted to keep this quiet she could certainly find a suitable “beard” to be photographed with. The artsy types would fill the requirement, and of course that would be the one time she is photographed, despite the fact that she is generally ignored.
I recall my wife’s friends at that time period. Those single after age 30 made a getting a hubby the prime purpose of their existence. Barbara is the daughter of an ex-president, the contacts at that level of society are such that a husband can be acquired. Look at Chelsea Clinton, how do you think she got her hubby?