From my experiences, it takes more than 10-15 minutes for the whole breeding to take place... as they will lock the male is swollen and it take several minutes up to a 1/2 hour for them to disconnect....
Now they can tie up in a second but the breeding process is a little longer. If she wasn't in heat I doubt she would even let a male try to mount her and she wouldn't have been ovulating... to become pregnant. Some false pregnancies can become serious for some females so if she is showing signs of this watch her closely.