I find this an interesting discourse. One that has or will affect 99.99% of all Jw's who ever leave the cult.
Previous posters have hit one of the nails clearly on the head. You must know what you want your relationships to BE.
It probably goes without saying that this relationship will never be quite the same no matter what direction you take it. My experience has been that most 'center core' Jw's [or those moving back toward center as your friend seems to be doing at the moment] have very little to talk about outside bOrg ideology. So the friendship might whither no matter what you try to do if you refuse her evangelical advances.
On the other hand, she is opening doors that you might use to plant seeds that may further open her mind over time. I would be tempted to think about [even jot down notes for quick reference] various things you expect she will say, and find clever and well thought out parries to her thrusts. This might be possible without invoking any of the standard cult defenses, since you two were, as you stated, pretty liberal in your thinking, had investigated outside the Watchtower box in the past.
The unfortunate side of this is clearly that her emotions [the one thing that is very tough to combat with logic of course] are deeply involved now with her son's return to the Watchtower fold. Since you two are distant now, both in terms of physical geography and ideology, she might find it relatively easier to throw you under the bus and to forge a solid with her son.
I am not you. But if I were you - I would simply ask her where she wants this to go? Then temper my response over time with her reply. She may be willing to be unconditional, in which case you can be yourselves and stay in touch, though I would imagine the friendship will never be what it was. She might just retract into her JW world, finding it easier to shut you out. In which case, as painful as this is, you would be better off over time. Since who can maintain any relationship based on 'mutual beliefs' if you don't have them anymore. {I know from where I speak with this, as I lost my absolute best friend, who happened to be my cousin, I was 'unconditional', he was all cult all the time.}
I wish you well. None of this is easy. Good luck.
Peace/Namaste
Jeff