The BHS textual apparatus shows a variation based on LXX.
7 a 𝔊 ἑσπέρας = עֶרֶב || b–b 𝔊 οὐ κατέπαυσεν ἐν τῷ ἀγρῷ = לאֹ שָׁבְתָה בַשָּׂדֶה
The difference may not actually be due to a textual variation. This is difficult to translate:
זֶ֛ה שִׁבְתָּ֥הּ הַבַּ֖יִת
מְעָֽט (in 2:7, MT)
If it means "and now, until she dwells in her house shortly," it may mean the same thing as the LXX. However I'm not finding it translated that way.
until now; she has been sitting in the house for a little while (NASB1995)
She has rested but little in the hut (JPS Tanakh)
except for sitting in the resting hut a short time (NetB)
with scarcely a moment’s rest (NAB)
and till now; she sat in the house a little (YL)
Many translations have the meaning that she didn't rest until then.
This translation seems particularly accurate. Apparently, Boaz waited until Ruth left to rest. Then, he asked his reapers who Ruth was. His reapers apparently told him more than given here because of what he later knew about Ruth. Later, whether after her return or at the shelter/house, he then talked to Ruth.
Now behold, Boaz came from Bethlehem and said to the reapers, “May the LORD be with you.” And they said to him, “May the LORD bless you.” 5 Then Boaz said to his servant who was in charge of the reapers, “Whose young woman is this?” 6 The servant in charge of the reapers replied, “She is the young Moabite woman who returned with Naomi from the land of Moab. 7 “And she said, ‘Please let me glean and gather after the reapers among the sheaves.’ Thus she came and has remained from the morning until now; she has been sitting in the house for a little while.” 8 Then Boaz said to Ruth, “Listen carefully, my daughter. Do not go to glean in another field; furthermore, do not go on from this one, but stay here with my maids.
9 “Let your eyes be on the field which they reap, and go after them. Indeed, I have commanded the servants not to touch you. When you are thirsty, go to the water jars and drink from what the servants draw.” 10 Then she fell on her face, bowing to the ground and said to him, “Why have I found favor in your sight that you should take notice of me, since I am a foreigner?” 11 Boaz replied to her, “All that you have done for your mother-in-law after the death of your husband has been fully reported to me, and how you left your father and your mother and the land of your birth, and came to a people that you did not previously know. 12 “May the LORD reward your work, and your wages be full from the LORD, the God of Israel, under whose wings you have come to seek refuge.” 13 Then she said, “I have found favor in your sight, my lord, for you have comforted me and indeed have spoken kindly to your maidservant, though I am not like one of your maidservants.”
(Ruth 2:4–13, NASB1995)
It is not necessary that the LXX translated from different Hebrew wording. It may be a matter of the LXX changing the wording because the Hebrew wording was awkward in Greek. Notice how varied the English translations of this phrase are.