K.C.
I think this is very fresh for you and I think you should give it a little time before making any decisions. Tell her honestly that emotionally this is hard for you right now and that if she's ok with it maybe you guys can talk about it in a couple of months. If she's been a friend for 15 years I'm sure she will totally understand. If she doesn't feel she can wait for an answer then tell her she needs to do what she needs to do for herself and her family and you'll understand if she needs to make other arrangments. Just don't leave her hanging. Tell her you'd like some time to heal and decide emotionally what will be best for you and you'll tell her on a specific date what your plans will be. I can't imagine anyone not understanding that. You may feel differently and perhaps may even get pg again sooner then you expect.
I'm very sorry for your loss.