I can well understand your feelings of guilt DSJ,it is a natural reaction to quite a sad situation.
Of course it is not at all nice knowing your young daughter is struggling so financially whilst also having a young child to rear with all the costs this brings.
However it would seem you are already helping out in several meaningful ways whilst,at the end of the day,you have been a hard worker and you too have a life to live.
It hurts knowing your daughter is home bound at such an early age ,however she is the one whom has tied herself down by having a young baby,and sadly sometimes these are the consequences.
By all means be there and keep reaching out to the best of your ability,whilst perhaps there are ways around allowing your daughter the odd day or night off............with you babysitting etc.
Guilt helps no one and I am sure your daughter holds nothing but praise for all you already do to help them both.