Since how long is this happening? Are you diabetic? Are you on any medications?
I apologize for the delay. My internet connection was not working. I am sorry, I kept you waiting.
Yes, the hormonal changes sometimes can be responsible for the night pain in the legs, though this is not the common reason. If she is overweight this may also cause ache in the legs during the night time because of the increased burden of work for the leg muscles.
The other possibility to consider is restless leg syndrome. A typical feature of this is pain and aching on lying down, which gets better on walking. Iron deficiency, diabetes are some proposed causes but many individuals do not show anything. Neuropathy and varicose veins should also be ruled out by your physician.
Read about it and its treatment;
Please feel free for your follow up questions.