Disclaimer: I don't own Veep and never will. No copyright infringement intended.
Selina Meyer's secretly glad she miscarried because she didn't want to go down that road again, not to mention the scandal that would have ensued. She would forever be grateful that Amy took the fall for her. It was a little cold hearted, sure, and she'd never forget all that blood, but she wasn't sad about anything.
Selina hated that she felt guilty over not being sad. She loved Catherine and her daughter was enough for her. One child had always been her plan. She has the right to feel the way she does, and she won't let anyone tell her otherwise. It's nobody's fucking business – especially those fucking idiots in her office – about how she feels.
She's also very grateful that she doesn't have to marry Ted or be tied to him forever. Selina's age was also a big factor in not wanting another baby. There's so many reasons this pregnancy was a bad idea, and she could list them forever. Despite the chaotic life she leads, Selina wouldn't trade it for anything because she's in a great and happy place. Eventually, the guilt will fade away.
Selina will move past this and get her life back on track.