Hello Swad13,
My grandmother was like that. CBS was her channel and "Murder She Says." No other channels mattered.
Is this a home or apartment? If you could, I'd install an
Antennacraft HBU11k http://www.solidsignal.com/pview.asp...t-%28hbu11k%29 Outdoors orientated to magnetic 326. There is enough signal from other stations, I'd expect to see many more even if not pointed at them.
If your mother wants WMUR only, then program her TV to only a couple channels (or single channel in this case). My mother's new samsung allows for "favorite" channels only to be selected in the menus. Then the channel button up or down only scrolls through the selected favorites. That may be an option.
I'm not a fan of indoor antennas. Even with plentiful signal, they may still be unreliable due to electrical interference and multipath. I'd hate to see you install a small indoor antenna then have hours of unending frustration and hers as well.
Thus, the HBU11k outdoors at magnetic 326 with the best line of sight possible in that direction in addition to programming your mother's TV tuner for her specific tastes is my recommendation.
Cheers.