girl holding out on sex

hello! so im writing this on behalf of my best friend. he has currently been dating the same girl for a bit over a year now, and the two recently got into a big fight and now that the smoke has cleared and seems like they are getting back on track, she is still holding back on sex (been a bit over a month now). so im wondering what are some strategies for him to get that back. he is usually really passive, so the advice i gave him is to be a lot more alpha and such so she isnt in so much control anymore. if there is any other advice people can give so i can pass over to my friend, youd help him out a lot lol. thanks guys.