As a mother, my opinion is that it is definitely
not maternal. I wouldn't leave my kids for such a long period, but if I was ever in that situation, then someone like Pete wouldn't be any kind of substitute.
The fact that she finds him attractive strikes off any kind of "maternal" connection. I find him attractive, and therefore wouldn't feel maternal towards him at all. You can't have it both ways.
In that situation, I would probably be more likely to feel maternal towards Glyn. 1. Because of his age. 2. Because of his naivety. 3. Because I don't feel the slightest bit attracted to him... and 4. Because he is a bit useless at stuff around the house, and could use practical help.
I just don't buy this maternal thing with Lea & Pete. She would shag him in a heartbeat if he was up for it.