Get to know her a bit, casual friendship/aquintance (depends on regular setting or common people you know), innocent flirting, lots of subtle ways to show you are interested, but wouldnt actively pursue someone who is in a relationship, unless its an unhappy one she's likely to get out of. Thats why its nice to have peeps you know in common, practical in feeding you such info

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But in general the ball is in the court whichever party who is in a relationship (aka end or not gonna bother) , not interested in entering a sitaution where you would aid in someone being unfaitful, unless its just a brief hookup/random fling, then dont care, but I mean in case its someone you are interested in starting a relationship with. Big ref flag IMO.
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She worked for like 10 days and disappeared. Then it took me 2 years to find her lol.