Hello T.: A little about me...mother of 4, 2 girls - 2 boys, married to my husband for 16 years and together for nearly 20 years...He's 42 and I'm 40.
Let's be honest...it is absolutely frustrating that our husbands lie to us, the fact is they do. Sometimes we have some intuition about things and we either hold onto it, follow through or we let the intuition make us insane...
His family may not have known that you were not in total agreement with the jacket, therefore I would not call or mention this to them at all. It's your business. It would only open up a can of worms that you may not recover from with the family. The niece probably called you to thank you for the gift card because when he gave it to her he told the niece it was from you...hence he would not have to explain anything to her about your finances and now the niece thinks you're amazing. Men are not smart enough to think through things and have a 16 year old lie for them unless he's a social path, which doesn't sound like the case. The niece probably thinks you two are the greatest right now because she walked away with theses gifts. She probably even thinks that you're very proud of her and she is deserving, besides she is 16, right. Also, it sounds to me like your husband did promise her the jacket initially. It was too specific for him not to have mentioned.
Advice: Men are sexual: women are emotional. Stand your ground be firm but sensual. Explain to him how it made you feel, made you look to his family and what it does to your relationship as a whole (trust factor), this is two-fold because you have to appeal to his vulnerable side while communicating, maybe in bed, after the baby is down for the night, when the stakes are high... Be blessed and don't let this incident ruin your marriage.