Yeah, she's definitely the one that's said it the least, for sure. But she's not been lacking in feeling love, she just... struggles to express it. 1400 years suppressing her feelings has done a number on her emotional expression, except for frustration and grumpiness, which she seems to have always had in fair amounts. And arrogance. Can't forget that self-assured attitude of hers throughout the ages. But love? Yeah, she definitely has closed herself off from that one for pretty much all her life.
Must be so damn awkward to suddenly want to express something you haven't even felt for all your over-a-millennia of living. It's why she's a damn 'blush-bomb'.