I think I am too old-fashioned to help with advice in the dating area...I still believe in letting them pursue you but today with texting and everything else...IDK!!!
And, I don't think there is anything wrong with keeping in touch with your SIL...in fact, I think it is great! Will be good for your S in the future in helping him stay in touch with your H's family and once you are D'd, she will just be your friend!
M48 H53 M16 T18 S16 D13 SS30 H drops bomb PA/8-30-09 H leaves 12-30-09 D filed by H 2-10 H asks to come home 4-11 Piecing