I know a few friends who have had IVF - and two who had stillbirths so can appreciate her desperation in having a baby, it can be soul destroying! She has put herself, relationship and body through so much!
How old is she out of interest? One friend was 42 when she finally had success with IVF
such a wonderful moment! still makes me cry with happiness for them!
I think the best thing to do is explain how you are planning your own family and that the time is not right - she may find that she will fall pregnant naturally if she stopped putting herself (and husband) under so much pressure and start to enjoy their relationship again (not saying she doesn't) but many do have issues afterwards.
Would she be interested in adoption? - so many unwanted babies
perhaps that is something to discuss with her.
There are people who offer surrogacy - perhaps if she is serious she could look into this - depending on how close your relationship is offer her as much help and support as she wants!
I would definitely say you are planning on starting a family so if you do get pregnant it will not surprise her. Also have an open honest conversation around how she may feel - if she wants distance, that is fine just never close the door on the relationship!
One of the hardest conversations I ever had was with my best friend - her IVF had failed and I had just found out I was pregnant - I live aboard so I had wanted to tell her face to face, my heart broke for her when she told me!
But she has had success now! 
Listen and support - ask her what she needs and have open honest conversation! x