Agreed. If that's where they were going with that story, and I believe they were, then Aunt Lydia needed to be portrayed somewhat differently.
For starters, she's not even overly religious. Yes, she's conservative and quotes the Bible and whatnot, but that's literally how millions of people act. She's certainly not Carrie's (of Stephen King's novel) mother. She knows Noelle is sleeping around and while she's not approving of such lifestyle (and frankly, a lot of irreligious people wouldn't be either), that doesn't bother her enough to stop her from seemingly genuinely bonding with her. I guess they wanted to show that she already had the tendency to "fix" women (her "You could be better!" line), like's she's doing now as an Aunt, but the way she goes about helping Noelle (trying to get her to get a decent job, settle down with a good man etc.) is simply incomparable with the monstrosity of Gilead's handmaid system.
Moreover, she's clearly very much into the principal and she's really not that perturbed about that fact. They're awkwardly flirting from the beginning. She's willing to go dancing. She's willing to invite him over and make the first move. If her "straying" is what sent her down the shame spiral, it would have been much more effective if she had made a pass on that man and he coldly and flatly rejected her (thus adding insult to injury), instead of clearly stating that likes her and wants to spend time for her, but is just not quite ready yet for something physical. Or alternatively, if they had had sex, and she liked it, but couldn't cope with it later, feeling she had betrayed herself - but for that, they would have needed to amp up her religiosity.
The way it was presented, it really looked like a tired cliche of a scorned woman going cray-cray, which does no benefit to anyone and is frankly insulting.
Also, what I found odd is that there were absolutely no hints that she was acquainted with Sons of Jacob and their ideology at the time, no use of Gileadean "Newspeak". One would think she'd already be well on her way of becoming a "true believer" at that point.