Let me explain how it feels (and the "oh well she can have IVF" line is hideously insulting to anyone who's infertile, as is the "well you can always adopt").
I can explain vividly how it feels - my SiL announced her pregnancy on Sunday. I'm infertile it appears (over three years of trying, one miscarriage - cannot afford IVF or fertility treatment and don't meet NHS guidelines). It feels like you've been kicked in the gut, and then someone's plunged their fist through your ribcage and started ripping out your entrails before tearing your heart in two in front of you. Society expects a certain response - and yet emotionally, you're in no way placed to give that response (it is a very very special, strong infertile woman who can be a doting auntie - I'm not that strong, and I bet even the strong ones sob in the car on the way home).
I've cut myself away completely from OH's family following the news - I've had to for my own sanity and self-preservation. If you're infertile - reminders of it are absolutely everywhere - TV, radio, newspapers (pretty much every week the DM runs an article aobut how childless women are selfish hedonistc beasts). You go out of your house - you're confronted with happy families - it's all a constant reminder of the world you'll never ever get to walk in, a reminder that you matter less in the world - and yes, there's jealousy in there, along with anger, rage, grief... none of these are very attractive emotions and, because inside you're basically a decent person, you get more and more angry at yourself and your body failing you - because you're thinking such dark, bitter thoughts.
That's what it's like every day (counselling doesn't help before anyone throws that one in - cheap wine is more use :D )... yet you can mentally shove it aside somewhat and function... until the pregnancy announcements start. Each one brings it all bubbling to the fore again (kind of like some ancient sealed evil that they never do the job of sealing it up properly in the movies) - you have to smile, say the right things and then go hide in the loos to cry and deal with your own grief. Then, when you've dealt with that - the baby comes along and rakes it all back up again. Add in the fact of it being a relative, and them giving parents a grandchild that YOU can't give them - and it's soul destroying to go through.
Every time there's an announcement you get torn apart by grief again and go through all the stages of grieving for the child you can't have, for the future you'll never see, for the grandchildren you won't have, that you'll never see your partner play with his son or daughter - and you go through it every single time... sometimes, if you're still trying, you go through it on a minor level every single month.
It's truly a pain that you will never have to endure - one you can't comprehend in how badly in seeps into and corrodes your life and relationship. You sitting there making comments aobut "she can just have IVF"... it's no panacea, it's hideously expensive, you don't know that she's not been through it already, or isn't suitable - it could be the quality of her eggs that are the problem, she could have been having repeated miscarriages and be struggling to actually carry a child to term - there are so many factors involved and you end up learning so much more than you ever thought you'd need to know about your internal plumbing... to fob her off with the IVF line - I'd have exploded on you at that point, she's been stronger than me that she's dealt with you having a son (I'd bet the girl's been the killer part of this to be honest).
You won't understand - I'll be jumped on and dismissed as the freak or abnormal, last time someone posted that they were dreading a family Christmas because of infertility/miscarriage/pregnant relation - they were called selfish and made out to be a hideous person on here... I'm not abnormal, go onto any long-term infertility forum on the internet (I'm not talking about "we've been trying for a baby for 2 months zomg nothing's happened yet", I'm talking about the true, long-term infertiles, the ones who've had the probes and needles shoved everywhere) and you'll find the same story every single time.
I've typed all that - but I doubt you'll understand it. You just see someone being "jealous" and "selfish".