I'm not sure what group this belongs in.

I'm just feeling a little down today.. So I just found out that my friend is expecting her 2nd child. She had her first when she was 17. Unplanned and happened because of forgotten birth control for 3 days. Now she's with a new man (I like him, they're good together) and expecting baby #2 because of forgotten birth control for a few days. She's 23 and lives in her parents garage with her son.. I'm having trouble being excited for her. I'm happy because she's happy but I'm struggling with how I should feel. We're married, stable, with a house of our own. We haven't been trying for long, but I just can't believe how easy it is for her... Am I a bad person or friend for feeling this way?