Vistor Visa for my unmarried sister - 1 previous rejection

[India2Pa]

Background
My Parents - both have visitor Visa and will be travelling to USA for first time in MAY
My elder sister – She is on H1 B Visa and pregnant currently . Husband is on H4
Myself – am on H1 and my husband is on H1
My YOUNGER SISTER SWATHI (UNMARRIED)– She completed her studies M.SC and currently working in a private company in (India) .
Brother(UNMARRIED) – Completed Btech and currently working in INDIA.

QUESTION : My YOUNGER SISTER(UNMARRIED) SWATHI had applied for Visitor Visa earlier a year ago and got REJECTED . My elder sister is pregnant and my parents will be travelling to USA In May .we want SWATHI also to come to USA for a visit so that it will be a great family re union for us.
What are the chance of Visitor Visa approval if she plans to appear foe a Visitor VISA again (based on 1 past rejection) ?
We are also looking US matching for her currently . so if she gets married to a H1 guy in future , she needs to appear for H4 stamping after marriage . Will there be any issue for H4 stamping on basis of Visitor Visa rejection‘s (1 in the past and 1 now if she appears again now and faces a rejection) ?
we are thinking for applying as a Family re union on the occasion of New born baby . Is there a better reason I can give if we plan to appear for a 2nd Vistor Visa for HER ?

[peace999]

young and single, with silbings in US and parents already have a visitor visa, the officers suspect exactly what you have in mind.
She might like to get married in US. So with one rejection already, it will be difficult for her to get a visa.

Positive factors that MAY help;
*If she has a history of travel abroad
*She is earning very well in her job and can show self funding of the trip
*Show a documented leave from her employer and show a short duration of the trip matching the leave
like 2-3 weeks.

A second denial of B1/B2 will not affect her future H-4.