How to respond to the ultimate guilt trip....

[Piratelvr1121]

Well I was just podding someone else, but I like that Amy Tan retort. 

It bugs me when people use religion as a guilt trip to push someone to forgive.  Having a toxic relationship with my own parents that are now cut off, I have heard the "Jesus says forgive!" Perhaps, but forgiveness does not mean I have to subject myself to being hurt over and over. 

Even my priest has said that forgiveness is good, but when we forget things, they tend to come around and get us again, and it is possible to forgive while protecting ourselves by putting up some distance between ourselves and those who hurt us.

[MrTango]

I think this is one of those situations where you can just look at the person as if they've just grown a third head, turn back to the person with whom you were conversing and resume the conversation as if the interruption had never happened.

[Twik]

I'd recommend saying, "I beg your pardon?!?" while looking at her as if you couldn't believe she would be so rude as to interject herself into your conversation. If she continues to lecture her, murmur, "Do I ... know you?" then shake your head and return to your own conversation.

[Thipu1]

It's possible to deeply love a person but not particularly like them.  This happens with parents and adult children all the time.  Yes, each will vent to friend's about the other but, in essence, the venting is innocent.   

For a remark like that in the OP, I'd just put on my Teflon jacket and shrug it off. The interloper does not and cannot know the family dynamic being discussed. 

On 'Patience' Gilbert & Sullivan had something to say about those who, 'Utter platitudes in stained-glass attitudes'. 

[BarensMom]

I'm afraid I was guilty of this when younger.  My parents had their faults, but I knew they loved me and tried to do their best, in their overprotective way.  My friend, Lisa, wasn't so lucky.  I couldn't understand why Lisa wished for her parents' deaths, even after she told me some of the things that happened to her because of their poor parenting.  I would respond, "but they're your mom and dad, how could you say that?"  Lisa would snort and tell me that I didn't know what I was talking about.

30 years later, I've grown up and know better to say anything to my less-fortunate friends, much less than complete strangers. 

[MrTango]

I'm afraid I was guilty of this when younger.  My parents had their faults, but I knew they loved me and tried to do their best, in their overprotective way.  My friend, Lisa, wasn't so lucky.  I couldn't understand why Lisa wished for her parents' deaths, even after she told me some of the things that happened to her because of their poor parenting.  I would respond, "but they're your mom and dad, how could you say that?"  Lisa would snort and tell me that I didn't know what I was talking about.

30 years later, I've grown up and know better to say anything to my less-fortunate friends, much less than complete strangers.

I don't think you were necessarily in the wrong here.  First off, if she was talking to you, then you weren't butting in on a conversation of which you were not already a part.  Second, it's quite a difference to complain about something one's parent does and wish for one's parents' deaths.  I think it's perfectly reasonable to express shock when someone expresses a wish for another person's death.

[BeagleMommy]

I would be so tempted to use the one eyebrow raise, Spock voiced "Fascinating" and then return to my conversation.  Either that or a flat "Hmmmm".

We all need to vent about the craziness that is family.  I love my parents, DH and DS with all my heart, but sometimes they just grate on my last nerve and I need to let it out.  That's what girls' night with my best girlfriends are for, right?

[Hmmmmm]

Them: "You shouldn't complain.  Mom's won't be around forever."
You: "Thank goodness for that!"
 

She/He was very rude for interrupting your conversation for any reason. My mom died when I was 23 and for a very long time I couldn't stand listening to anyone complain about their parents, especially for something I found to be trivial, but I never said anything. (Well once but that was to a co-worker who said planning her wedding would be so much easier if her mom was dead. And I responded "why don't you share that sentiment with her, maybe she'll oblige you." and I still feel bad about saying it 20 years later.)

Comments like hers are in the same realm of over hearing someone complaining about a flat tire and a stranger replying well at least you have a car.  Really not their business.  Or hearing a mom complaining about their child's messy room and someone remarking at least you have a child

[wolfie]

I hate the cousin of that one "I would give anything to have my mother around to snoop through my purse/critique my clothes/whatever you are complaining about  just one more time"

[CrochetFanatic]

Eavesdroppers need to butt out.  Once or twice, I've responded with the glacial stare and, "This is a private conversation."  Of course, they were very offended, but it was none of their business.  This person didn't know you, and apparently didn't know her place.

[Amanita]

In regards to the whole forgiveness thing, and how so many people are pressured by those around them to "forgive and forget", a book of mine has this to say:
"Forgiveness is earned by repentance. To forgive somebody who has not changed their behavior is to condone violence. (or whatever bad behavior)