I'll tell you.
I sensed a closeness there beyond simple respect. Riley was SO upset when he found out Maggie had tried to kill Buffy. It was like he was personally offended. Like a family member had betrayed him, not simply someone he respected.
Now, everyone knows Maggie had a close relationship with Riley, and that he was her favorite, and many fans believe she saw him as a son. I think Maggie was in love with Riley, personally. I believe Riley was oblivious to this. Why do I think Maggie was in love with Riley? Mostly because of what Lindsey said about her role;
The "potential something" "that's slightly out of her reach" is Riley. Maggie's referring to a wishful romance with Riley - which of course she can't have because it would be entirely inappropriate because of her role as his teacher, supervisor, and mentor. Not to mention he was in love with Buffy. Of course Maggie was jealous. This theory makes why she tried to get Buffy killed a lot more understandable.