I dont agree RustyV, but thats only my opinion, theres no right or wrong but different ways to see it.
for me, its F that push D into sharing. theres no D that explores her independents and curiosity to try other dudes.
D is in love and she is following F, she trust in him completely, that is also why they need to talk when she is unsure, and thats also when F can decide how to move forward. of course once you push her into a direction she will be more open for what it means. if F show agreement when Martin is giving her compliments, that will tell D that its ok, not something bad.
I can not see D dating other people, its impossible right now. F is very important to her to feel secure.
but I can see F pushing D to try things, to be more open for that, to relax when other dudes gives her compliments, to allow someone to take pictures etc. but everything would crash if they would break up. D would not feel free to date around. She is not there, its too early, and F is too important.