Juliana Noel, Lady Alington (1646-1667) was the daughter of Baptist Noel MP, who represented Rutland in the Short and Long Parliaments, and was in arms for King Charles I. He compounded for £9,000 in 1647. (The Short Parliament was in 1640, and the Long Parliament was from 1640-1653; the MP biographies of which are expected "around 2020".)
On Baptist Noel's death in 1682, he was buried in the church of St. Peter and St. Paul, Exton. His grave is marked by a fine marble tomb by Grinling Gibbons, dating from 1685, showing the Viscount with his fourth wife, Lady Elizabeth Bertie, and carvings of his 19 children. He was succeeded by his eldest surviving son, Edward Noel MP, who later became 1st Earl of Gainsborough.
So Juliana Noel, Lady Alington's oldest brother, Edward Noel, was an MP. The early part of his Parliamentary biography is helpful:
Edward Noel was bap. 27 Jan. 1641, 1st surv. s. of Baptist Noel, 3rd Visct. Campden by his 3rd wife, Hester, da. and coh. of Thomas, 2nd Baron Wotton of Marley;
Edward and Juliana's other brothers included: Hon. Henry Noel MP
and half-brothers Hon. Baptist Noel MP and John Noel MP.
Edward Noel m. (1) by 25 May 1661, Lady Elizabeth Wriothesley, da. and coh. of Thomas, 4th Earl of Southampton, 2s. (1 d.v.p.).
So Juliana Noel and William Alington's sister-in-law at the time of the Diary was the daughter and heir of the Lord Treasurer.
One of Juliana's sisters was Catherine Noel, who in 1673 will marry Lord Roos, whose divorce from his first wife we have been following.
Another sister was Mary Noel, who married James Compton, 3rd Earl of Northampton.
Another sister, Elizabeth Noel, married Charles, 2nd Earl of Berkeley
You get the idea ... there are 15 more siblings to look up, but to say Lady Alington was well connected puts it mildly.
Chart showing the number of references in each month of the diary’s entries.