If she's running with the boar and coming into heat, then she would definately 'let him'!! but it would be unusual for her to take if she's been empty for so long, hence why no piggies so far even though there is a boar! unless of course the boar is a 'jaffa' so to speak!! Has he fathered any before? to go down the AI route is fairly straightforward if you know when she is cycling, and not a lot of money to part with, around £25. I know of some kune x old spots that produced nice, if a bit small, porkers. If you are confident that she is fit and well then I suppose you could try, although I'd pretty much be sure she's barren, sorry! but keep us posted as to what happens!
As a thought, have you seen him actually mount her? if you rub some marker ink (sheep raddle crayon/ink) on his chest then you'll know if he's done it! My pigs just keep 'at it' for about 2 days, usually when theres spectators so I know the deed is done!!