Female Bettas lay eggs, they don't actually carry babies in them :) Horizontal stripes means shes stressed out, something could be wrong with her water, someone may be picking on her or if she's new she might be getting used to the place :) You'll have to give us more information to let you know what's going on with her.
evilvog hope you are not taking them as if there rude, are you planning to spawn them correct? how long have you had her in the vase/container in the spawning tank with the male, (make sure the male cannot get through that vase/container
Most, if not all, fish has 2 egg sacks incl. bettas. Females will always carry them since the day she becomes sexually mature regardless whether she looks fat or thin. These eggs will "ripen" and ready to be released when she goes into spawning mode (either sense male's hormones or see male's flirting). But sometimes she releases and eats them for no apparent reason.
When conditioning pairs for spawning, IMO it's best not to let them see each other continuously. You can flare them from time to time to see their reactions - to see whether they flirt or not, but not too long. Because
1. female might release her eggs,
2. female might become stressed,
3. female might see the male as a rival rather than a mate,
4. Male might get frustrated and change into "killing" mode instead of breeding.
To determine whether a female accepts a male or not or whether she wants to spawn is usually shown by her vibrant colors, often with the so called breeding bars (light colored vertical bars). And she will most likely swim in a flirting fashion like the male. If she doesn't show these signs, you might need to condition her further.