Amber was pretty hyper and Matt seems very, very mellow. It might have been nerves on the wedding day for her, but he overall seems like a very mellow dude. If she gets amped up when she gets nervous or excited, she might feel like he's not getting excited enough when really, he just doesn't express emotion the same way she does. I've seen that dynamic play out before. I wonder if she's an extrovert? He seems like an introvert. That can work, but it takes a real understanding of the way each person functions, which they don't have yet.
I get the impression that she has not had a romantic life of any kind for ten years. No dates, no hookups, no situationships, no flings, nothing. If she had had no committed relationship for ten years but she'd been going on dates, hooking up, being involved with people but not being "official" with them, etc. that would be one thing, but I really get the sense that she just shut that part of her life off altogether. The way she talks about how she put up walls makes me think that. She also tries to spin it as though she was too busy dating herself to date other people, but it sounds to me like she had a pretty standard life. She went to college, worked, got a master's, traveled ... all good things, but it's not like she was SO busy that she couldn't eke out time for a date now and then. If what happened in her high school relationship was so hard for her to get over that she'd completely shut herself off like that, I think she needs a therapist, not a husband. You saw Greg's "zoinks!" face when she told him.