According to Lindsey, as quoted by Constable in the NET Bible Notes, yes, Samson was poking fun of his bride-to-be:
“In calling her a ‘heifer’ he was ridiculing her for her untamed and stubborn spirit (cf. Jer. 50:11; Hosea 4:16).”
In Jeremiah 50:11 the prophet describes a heifer (or calf) as follows:
. . . because you frisk like a calf in the grass . . . (CJB)
And in Hosea 4:16, the prophet describes a cow as follows:
For Isra’el is stubborn as a stubborn cow . . . (CJB).
Assuming the above observations about the behavior of at least some cows are true, Samson was indeed describing his bride-to-be as a recklessly carefree cow who couldn't foresee how her behavior toward her husband-to-be would spoil the marriage even before it was consummated, which traditionally happened at the end of the seven-day feast.
As for a cow's stubbornness, here is what a modern-day dairy farmer has to say about cows in general,
Cows are large animals, and while they are not generally aggressive, their size can be intimidating to someone who is not used to working with them. Furthermore, while cows are very intelligent, they can be very stubborn sometimes. They also have a much higher pain tolerance than people do, meaning that using mild pain to get a cow to do something is usually not effective, and an inexperienced person will naturally attempt to escalate pain to get the desired response. This is not the right response, but a natural and understandable one.
Obviously, then, Samson's Timnite bride-to-be was very stubborn indeed, and for good reason, I might add. Her well being and the well being of her family were at stake, since the groomsmen's extortion does not appear to be a mere bluff. Her constant nagging, pleading, and crying finally exasperated Samson to the point where he told her the answer to the riddle he had proposed to his groomsmen.
Should Samson's metaphorical remark, then, be interpreted as derogatory? I think so, given his state of mind after having lost the bet with his groomsmen. However, his insult was evidently uttered in ignorance of what was at stake, humanly speaking, for if his bride-to-be had not pried the secret out of him, her family could have died!
In conclusion, had Samson been a little more sensitive and diplomatic with his Timnite bride-to-be and had pried out of her the reason for her importunity, he would not have had to travel the 23 miles from Timnah to Ashkelon to exact retribution on the wrong Philistines!