honda makes the rebel 250, yamaha makes the virago/v-star 250, and suzuki makes the boulevard s40, all lauded as good beginner friendly cruisers. personally I really like the look of the Virago 250. and unlike many of the newer members here, your sister’s small size and weight will mean she won’t be saying “I need an 1100cc bike because those little 250s are just too cramped) they also have the advantage of having amazing gas milage.
like spaz said, or at least from EVERYTHING I’ve read, cruisers have in general less power per cc than sportsbike, so you can go a bit higher without worrying about accidentally screaming 100+ uncontrolled down the highway, however they come with a much larger increase in weight the more cc’s you’ve got, and that could be a real issue with as small as she is. if she drops that shadow, she’s going to have a hell of a time lifting it back up, and even if her husband is there to help get it back up, it’s going to have a serious psycological effect if she can’t right her bike herself when/if she drops it. and if she’s as uncomfortable as it sounds, then she’s very likely to drop it.
sounds like the hardest one to sell will be the hubby, some people get set in their mind what others need to have, regardless of the wishes or concerns of the other person. hopefully he can overcome that and get his wife what SHE wants, not what he wants her to want.