Baby gift giving etiquette - Am I out of line?

My sister in law is pregnant. The dad took off, so she gets no help from him, and her kids are teenagers, so she's starting all over.I found a great deal on a travel system for her, asked if she liked it, she said she did, and I bought it for her while it was half price. She was happy and thanked me, but... show more My sister in law is pregnant. The dad took off, so she gets no help from him, and her kids are teenagers, so she's starting all over.I found a great deal on a travel system for her, asked if she liked it, she said she did, and I bought it for her while it was half price. She was happy and thanked me, but asked me 12 hours later if I could cancel my order because her coworkers said they had planned to get her a travel system and she didn't want to hurt their feelings. Luckily, I was able to cancel the order, but now I'm offended and my feelings are hurt. My husband said she probably just wanted to pick out her own stuff because she has a shopping addiction. I feel as though she didn't appreciate the gift in the first place. Am I overreacting, or are my feelings reasonable?
Update: Edit - I failed to mention that she is my husband's sister.
Update 2: A travel system is a stroller/car seat combo.
Update 3: Her coworkers have not yet purchased anything, so I don't see why I had to cancel my purchase when she could have told her coworkers that someone had already purchased the stroller/car seat combo for her, but there were plenty of other things that she could use.
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