No...? I also think the perception that "Taeyeon only loves Tiffany" is perpetuated by the fandom more than anything. There are plenty of moments where she shows love for the other girls. For instance, I LOVE the Taeyeon/Sooyoung moments in "Channel SNSD" (when Taengoo chose to go in Syoung's car; when Syoung cheered for Taeng during the boat race) or even Yoona and Taeyeon's "Cuties!" team (and didn't Taeyeon choose Yoona as her teammate and vice versa?).
I also think that given Taeyeon's reserved personality, she's not the type to "voice" her feelings like Tiffany does. I'm sure by nature, Tiffany brings a lot of that out of her as well.