Pretty well every novel ever written about Edward and Isabella, and a few works of non-fiction too, features a Compulsory Scene wherein the young queen is horrified, shocked and distressed to see her new husband embracing and kissing Piers Gaveston, who is, she now realises, her husband's lover. According to the St Albans and Bridlington chroniclers, Edward did indeed "run to Piers among them, giving him kisses and repeated embraces; he was adored with a singular familiarity. Which special familiarity, already known to the magnates, furnished fuel to their jealousy."  Whether Isabella saw this happen, however, is highly debatable, as she and Edward came ashore from their ship in separate barges, or perhaps had travelled all the way across the Channel separately, as this entry on the Fine Roll  makes clear:
"Be it remembered that on Wednesday after the Purification, 1 Edward II, the king, returning from beyond seas, to wit, from Boulogne-sur-Mer, where he took to wife Isabel, daughter of the king of France, touched at Dover in his barge about the ninth hour*, Hugh le Despenser [the Elder] and the lord of Castellione in Gascony being in his company, and the queen a little afterward touched there with certain ladies accompanying her."
*i.e. around 3pm.
Most likely, by the time Isabella arrived 'a little afterward' the embracing and kissing had already finished. Regarding Edward II's behaviour on seeing Piers Gaveston again for the first time in, ooooh, ages (actually it was only sixteen days), it is not automatically the case that he was greeting his lover and everyone knew it. It was not the kissing and embracing themselves that were the problem or that caused shocked, offended comment – the early fourteenth century was a tactile age and kissing on the lips was a common way even for two men to greet each other, with no necessary implications of sexual desire – but that Edward singled Piers out for special attention and kissed and embraced his friend more than he kissed and embraced the other barons. 
What Isabella thought of Piers Gaveston, then or ever, is impossible to say for sure as we have no words of her own on the subject. There is a widespread assumption nowadays that Isabella must have hated and resented Piers, and seen him as her rival for her husband's affections and as somehow 'taking her rightful place', but this is merely speculation with no evidence behind it, however often the notion is given spurious credence by being repeated in books and on television *cough Helen Castor cough*. It is of course entirely possible that Isabella did dislike and resent Piers, but it is emphatically not a certain fact. On 29 October 1311, a few days before Piers was forced into his third exile, Isabella sent a letter to the receiver of Ponthieu, the revenues of which county which Edward had granted her a few weeks after their wedding in 1308, "concerning the affairs of the earl of Cornwall."  Apparently she had agreed to help Piers in his exile, at least financially, and perhaps in the naming of him as 'earl of Cornwall', which title had been stripped from him, we may see some sympathy on Isabella's part to her husband's 'favourite'. Or possibly Isabella was thrilled that Piers was being sent into exile yet again and considered naming him 'earl of Cornwall' and giving him some money a small price to pay to be rid of him. I have no idea how Isabella felt about Piers, and neither does anyone else, whatever they might claim and state as fact.
1) Johannis de Trokelowe et Henrici de Blaneforde Chronica et Annales, ed. H. T. Riley (1866), p. 65; J.S. Hamilton, Piers Gaveston, Earl of Cornwall 1307-1312: Politics and Patronage in the Reign of Edward II (1988), p. 47; Gesta Edwardi de Carnarvon Auctore Canonico Bridlingtoniensi, in W. Stubbs, ed., Chronicles of the Reigns of Edward I and Edward II, volume 2 (1883), p. 210.
2) Calendar of Fine Rolls 1307-1319, p. 14.
3) See Jochen Burgtorf, 'With my Life, his Joyes Began and Ended: Piers Gaveston and King Edward II of England Revisited', in Fourteenth Century England V, ed. Nigel Saul (2008), pp. 46-47.
4) The Household Book of Queen Isabella of England, ed. F. D. Blackley and G. Hermansen (1971), p. 208.