Awwww, $nack loves you.
I had one of those that I tried and tried and tried to completely ignore. We just couldn't bring in another one at that time. The she started filling out and looking like she had a balloon inflating in her belly. Poor thing was already an amaciated kitty. Others were feeding her and then she would come back to my front porch. Silly kitty.
Here's my amaciated, pregnant kitty that cost me the price of her visits and the cost of 6 spay/neuters including hers(for my piece of mind)--
She repays me thousand fold with her love. And, as you can see, she is no longer amaciated but quite the opposite.