It certainly is a tough position to be in. Sophie has found your home - and your love - but unfortunately the reality is that you have to look at the financial side of things as well. Are you in a position to be able to make things work for all her future care? If you can foresee somehow finding a way - then keep her! However, if there's any doubt, you can't let your heart rule what is best for her... she deserves/needs to be guaranteed not only love, but any other care she may need in future. Good luck with your decision! Sophie sounds like she'd be easy to fall in love with!
Marj - Over the past few months, I've read your posts pertaining to Lady - and I must say, I admire how well you have taken (and are taking) care of her. Lesser people would be tempted to abandon their little one if the costs were so astronomical but your dedication, love and foresight are admirable.