In Uncanny X-Men (Vol I) #244 Jubilee tailgates through Gateway's teleportation window from LA to the deserted Australian outback town where the X-Men have set up headquarters.
She remains there in hiding until after the remaining X-Men (Psylocke, Colossus, Havok, Dazzler) enter the Siege Perilous in Uncanny issue #251.
In Uncanny #248, evidence is presented that Jubilee has been swiping food from the X-Men's reserves when Colossus notices their food supply is lower than it should be. And then Jubilee is shown raiding the pantry later in the issue.
In #245 Psylocke (Betsy Braddock) is shown on guard duty for their HQ (presumably psi-scanning the area). And in #248 she performs a "Full intensity" psi-scan on the surrounding area while looking for Storm.
So my question:
If Jubilee was in close proximity to the X-Men for days (or weeks) in the deserted Australian outback, and Psylocke was often performing psi-scans of the area, why didn't Psylocke ever notice Jubilee's presence?
The X-Men were generally on high-alert throughout these issues as they feared attack by the Reavers. It seems unlikely that the telepathic Psylocke would either not notice Jubilee's presence or decide to keep this information to herself if she did notice. A failure to disclose this information to the team could put the carefully-guarded secret of their existence and operations in Australia at risk.
Additionally Jubilee was just a teenage kid. As established in earlier issues of Captain Britain involving the Warpies (British children mutated by the remnants of Jasper's Warp), Betsy Braddock had an affinity for kids. If Betsy noticed the presence of Jubilee stranded in the desolate Australian outback, she'd be likely to want to help Jubilee survive.
It seems very unlikely that Psylocke would have noticed Jubilee yet decided to keep the information private.