I can see Jen being INFJ, ENFJ, or ESFJ.
These are my observations from a skim of her blog:
-Ambivert - she may just be slightly one or the other but not CLEARLY introverted or extraverted
-pretty strong use of Fe; i think it's pretty distinctive - seems very, very "FJ"
-doesn't seem to use a lot of Si; doesn't ruminate a lot on the past or make those kinds of associations with events
-doesn't seem to use a lot of Ni, either; I don't see much "universal symbol" stuff happening or images of the future (though she does project future images in private conversation)
-I see both Ne and Se. Lots of Se, actually... lots of "this is what I did today" recording with occasional analysis of what the experience might mean
Cafe's blog, to compare, also has a lot of "this is what I did today." I see a little more Ne and Ni there, but the Se is strong there as well. I feel like Cafe is pretty much a posterchild for INFJs, which makes me think that perhaps there's a developmental reason the blogs are that way as opposed to my somewhat angsty INFJ analysis-ridden blog. One reason might be that I have no husband or children, so all I have to do is think about myself, whereas Cafe and Jen's lives are very much consumed with motherhood/marriage.
I wouldn't rule out ESFJ for Jen. I'm fairly sure she's not ISFJ because she doesn't remind me at all of my mother (who is very ISFJ). But I wouldn't rule out INFJ or ENFJ either. In order for the conversation to be truly PRODUCTIVE, though, it's really important that people get over the "sensors are stupid" thing, because if it is the case that Jen is an ESFJ, it is concurrently the case that she's bright and witty.