Queen Mallika story and stream entry
In AN 3.86 it is taught that a stream enterer will be born in human and deva realms for a maximum of seven life times:

&quot;[Some,] with the wasting away of the three fetters, are
'one-seed-ers' (ekabijin): After taking rebirth only one more time on
the human plane, they will put an end to stress.
&quot;Or, not breaking through to that, not penetrating that, with the
wasting away of the three fetters they are 'family-to-family-ers'
(kolankola): After transmigrating &amp; wandering on through two or three
more families [according to the Commentary, this phrase should be
interpreted as 'through two to six more states of becoming'], they
will put an end to stress.
&quot;Or, not breaking through to that, not penetrating that, with the
wasting away of the three fetters they are 'seven-times-at-most-ers'
(sattakkhattuparama): After transmigrating &amp; wandering on among devas
&amp; human beings, they will put an end to stress.&quot;
AN 3.86 

In Great Disciples of the Buddha: Their Lives, Their Works, Their Legacy, by Nyaponika Thera it is mentioned that she wasn't a stream enterer at the time of her death. He gives the reason for her birth in hell as:

When Mallika died her twofold transgression-her sexual contact with the dog and her mendacious attempt to free herself from blame-caught up with her and brought about a rebirth in hell.

and later he says,

Although it was a very short-termed sojourn there, one can see that Mallika had not yet attained stream-entry during her life on earth...