Her frill is a bit odd, as if it were more decorative than defensive. The napeshield of the Triceratops was there to protect the back of the neck from being attacked. Since Tria's seems to point upwards more than back in most shots (and her appearance has been far from consistent, thank you very much, animators), it seems to be more for show than for her own protection.
Also missed by many is that she is a pink female dinosaur. While this may make it easier to distinguish between male and female, doing this has been totally unnecessary for most of the female characters. Littlefoot's mother, Dil, Ducky's mom, and Petrie's mom are just some of the characters which need no pink shade to mark them as feminine. Also, Tria seems to have some sort of a "mask" on her face, a white series of markings near her eyes. That alone would have made her look different from her mate, even if her shading was not too dissimilar to his (keeping in mind that Littlefoot's grandparents have similar shades, as do Littlefoot and Ali.)
One thing is for certain though; she is not at all like her mate. Perhaps she is "too opposite", in that Topsy is overtly masculine and Tria is stereotypically feminine (and yes, that includes the gender-shared duty of fighting to defend the children as much as it means the female enjoys relaxing in warm mud). Let's be glad they don't have nail polish and makeup back in her day, lest we have a "big-lipped crocodile" (alligator?) moment. Her "mask" almost looks like makeup, in my opinion, as if someone had painted her pink face around the eyes. Nevertheless, it is refreshing to see a female Triceratops who is not a tomboy. XD
EDIT: How vulnerable could a several-ton dinosaur be? She's not nearly as strong as her mate, but even if she were totally out of shape, she could easily overpower a human. I find it interesting how she only knocked a raptor back a short distance using her whole force, but Topsy could send one literally flying using only his head. And she tells him that she "loves it when he acts all brave." That part is not really bad, though. I see nothing wrong with a female being attracted to a strong/brave male, especially one who comes to her rescue. She probably couldn't beat that raptor; Tria said she could "maybe" handle it, and had a very nervous expression, but Topsy showed up to save her and the rest, before the other residents arrived to drive them out.
